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Insulating of Old Houses
Sally Nelson

  1. Introduction
    1. The Old House and Energy-Efficiency: A Perspective
    2. Insulation Problem Areas in the Old-House
  2. Heating Requirements and the Old-house structure
    1. Moisture condensation in old houses
    2. Recapulation of problem area
  3. Solving Insulation Problems in the Old House
    1. Conservation within the living space
    2. Structual solutions to the heat loss problem
    3. Instaling insulation
  4. Eliminating the moisture condensation problem
  5. Conclusion

1. Introduction

On October 6, 1977, Greater Portland Landmarks, Inc., Citizens for Historic Preservation, and the Maine Historic Preservation Commission, co-sponsored a workshop: Insulating the Old House. The workshop was originally conceived by the Advisory Service of Greater Portland Landmarks to address specifically the glaring problem of heat loss in old houses. As the evening's discussion demonstrated, this subject encompasses not only insulation strategies, but also analysis of the inherent energy-efficiency of old houses, the adaptability of old structures to modern standards of comfort and efficiency, and the importance of conserving the character and fabric which define the old house. The situation is complex and at times controversial. The purpose of this handbook, one of the first available on the subject, is the clarification of the issues, by emphasizing particular characteristics of the old house, identifying problem areas, and suggesting possible solutions.The handbook is based on the contributions of each of the four workshop panelists: Andrew Ladygo, architectural conservator, H. Alan Mooney, P.E., president of Mooney Engineering, Charles G. Wing, president of Cornerstones —school for energy-efficient housing, and Christopher Glass, architect, as well as the discussion initiated by questions from the workshop attendees. Publication is made possible by grants from Citizens for Historic Preservation and the Maine Historic Preservation Commission.[top]
2. The Old House and Energy-Effiency: A Perspective
Establishment of a comfortable interior space that provides shelter from the elements is the fundamental premise of all human dwellings. Historically, the maintenance of this environment through the efficient utilization of existing energy sources has depended upon strategies of siting, design, and orientation, as well as mechanical contrivances. Twentieth century innovations have promoted push-button solutions to the age-old problem of maintaining a comfortable living space.This subsequent era of reckless energy consumption, recently aggravated by exorbitant fuel prices and a recognition of the limits of the resources, has culminated in a re-evaluation of energy use and efficiency. The emphasis has shifted to economical conservation.In this context, the old-house owner can take advantage of the pre-technological character of the old house those elements of plan and design to which the living space was naturally accommodated in order that comfort and stability might prevail. These traditional principles of energy-efficiency revolve around two architectural concepts: enclosure and orientation. Enclosure refers to the actual structure and the living space it creates, while orientation connotes the siting of the house and the organization, the placement, of various activities within the house.

Early dwelling construction in New England illustrates the adaptation of certain elements of enclosure and orientation to the realities of climate and landscape. The traditional domestic architecture of England was the model for the first houses built by the colonists. These designs soon proved un-suited to the harsher environmental conditions in North America.Consequently, building sites were chosen that would assure a reasonably dry cellar. The facing side of the house was oriented toward the south to accept generous quantities of sunlight (heat); the long, sloping roof-line was a shield from the northerly gales. Sliding shutters and later, more decorative, folding shutters, minimized the loss of generated heat through the windows.

Many early houses standing today exhibit instances of attempts to control heat loss and drafts in walls and attics. Brick nogging appears regularly in the earliest of homes; quantities of corn cobs and sawdust are frequently found beneath attic floors and within the side walls. In later years, newspaper was used to seal large cracks and was often folded or crumpled to block a drafty space, an early example of loose fill.Nevertheless, the problem of energy-efficiency is particularly severe in old houses. Inasmuch as the historic character of the house includes traditional energy-efficient design solutions, that same age factor also implies certain complications for the old-house owner. Foremost among these complications is the very nature of the building, the soundness of its structure and fabric. Deterioration of the building materials, the result of weathering, vandalism, or lack of proper or careful repair, is a primary reason for substantial heat loss, which, in turn, precludes energy-efficiency. Moreover, as the builder of the old house did not have access to today's sophisticated techniques, tools, and materials, a relative lack of "tightness" in the construction contributes greatly to the heat loss factor. In addition, the old-house owner must como to terms with the different comfort levels tolerated before the age of inexpensive central heating. The original owners of the house, accustomed to harsher living conditions, accepted their dwelling accordingly.The severity of the heat loss problem is only the initial concern in old houses. The very solutions to this problem, either ill-conceived or carefully planned, may lay the groundwork for unforeseen and irreparable damage to the historic structure. These potential complications arise from an incomplete understanding of the new materials, their properties, and the consequences of "meddling" with the structural integrity of the old house.

It is the responsibility of the owners of old houses to educate themselves as to the current techniques of attaining energy-efficiency, to investigate the structure and fabric of their old houses, and to assess the particular aesthetic and historic qualities which distinguish their houses. The owners must be aware of any inherent elements of energy-efficient design as well as of the immediacy of the heat loss problem. Throughout, the owners of old houses must exercise caution in dealing with each fragile and irreplaceable resource.Thus, the historic perspective comes down to the peculiarities of the individual house and the responsible assessment by the individual owner, The following pages present technical information and analyses of typical problems as an aid in the education process. The discussion of solutions presents the alternatives available to the old-house owner, and the concluding statement provides a focus for the determination of the individual approach.(top)
3. Insulation Problem Areas in the Old House
The identification of insulation problems requires investigation of both the existing means of heating the interior space and the condition of the shelter. It is essential that the old-house owner take an active part in this investigation and analysis as the final responsibility for maintaining an energy-efficient house rests with those who make it their home. A well-insulated house can be an expensive house to heat if outmoded equipment is not replaced or windows and fireplace dampers are carelessly left open. The owner must be aware of the nature of the shelter and the contingent requirements for achieving energy-efficiency.

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Heating Requirements and the Old-house Structure

The condition of the existing heating system is a crucial factor in the maintenance of a comfortable and efficient living space. In old houses, the heating systems are often old and 'ineffective. The consequences, imperfect combustion and poorly regulated draft, account for substantial losses of heat. In cases of modified systems (i.e. coal furnace to oil burner), the heat exchanging surfaces may not be suited to the type of fuel burned.After the heating plant, one must consider the condition of the structure and fabric of the old house. In most cases this is the crux of the efficiency problem: heat loss and infiltration due to loose, drafty construction. The following analysis is based upon home inspections conducted by Mooney Engineering, Chartered, Professional Engineers and Consultants of Yarmouth, Maine.Although it is virtually impossible to describe a typical example because of the unique qualities which distinguish each old house, the models which follow illustrate common situations of heat loss and infiltration. Each model indicates the total heat loss, given the specified conditions, and the relative significance of each source of loss or infiltration.In the diagrams on the following pages, a scheme prevails which is presented in the abstract below.

 

A. 1-story house 30' x 50', 210 sq.ft. of window (old/loose), 2 doors (old/loose), full basement
B. 2-story house 30' x 50', 380 sq.ft. of window (old/loose), 2 doors (old/loose), full basement.
Numbers 1-4 represent heat loss as a percentage of the totalat the analysis conditions.

  1. attic/ceiling loss
  2. wall loss
  3. basement/floor loss
  4. direct window and infiltration loss
Number 4 is the critical figure; the large proportion of structural openings in the old house is the first indication of a problem in maintianing energy-effieny. The figure is based on the worst conditions of the window looseness with old, poorly maintained windows. COPYgif It is clear that the greatest amount of heat loss occurs through the ceiling and a combination of escape and infiltration through and around windows and doors. A comparison of the two houses suggests that the latter problem can take on an over-riding significance.The second pair of illustrations describes a more common situation, in which some steps have been token to minimize hoot loss, specifically, storm doors and windows and 3'/2" of fiber glass ceiling insulation, the customary procedures recommended 5-10 years ago. This amount of insulation has drastically reduced the attic heat loss. The losses through the walls and basement remain in the same range. however, the heat loss and infiltration through windows and doors assumes even greater proportions.

In the final situation, considerable work has been done to upgrade the energy-efficiency of the old houses. These measures have effectively minimized heat loss through the attic and walls.

Consequently the overall heat loss is overwhelmingly attributable to the absence of weather stripping.The old-house owner must draw the following conclusion from the preceding succession of examples: The inherent weakness of the old house, in terms of energy-efficiency, is the large proportion of structural openings. This is the most significant, but certainly not the only problem area.

As indicated in the illustrations, the other problem areas of the old-house structure are the attic (roof), side walls, and the collar. In each case the problem lies in loose construction and the nature of the historic materials. The fact that any heat within the structure will rise assures the significance of attic end roof losses. On the other hand, cellar losses below grade are loss significant because, as the soil temperature rarely drops below 40F, the differential between the two sides of the wall is minimal. However, cellar walls and foundations above grad.. are a serious problem. Masonry surfaces are poor insulators and conduct heat readily. Fieldstone Foundations, having lost much of their mortar, become primary sources of drafts.(top)

Moisture Condensation in Old Houses

Before attempting any solutions to these heat loss problems, the old-house owner must carry the physical and structural analysis one step further. Disregarding this aspect of the insulation process jeopardizes the future stability of the house.The purpose of insulation is the regulation of the flow of heat between the inside and the outside of the house — ensuring a comfortable temperature range within the living space, year-round. Storm doors and windows and weather stripping accomplish this by the actual blockage of cracks and other drafty openings. Materials such as fiber glass batting, shredded cellulose, and foamed plastics are utilized as space-filing insulators because their physical characteristics inhibit each means of heat transport: conduction, radiation. convection. Those insulation materials take the place of air spaces through which heat naturally diffuses.If dry heat were the only factor to confront, insulating the old house would not be a complex problem. However, the gaseous state of water, water vapor, is a natural component of air, as are hydrogen and oxygen. The amount of water vapor in the air, expressed as pounds of water vapor per pounds of air, is commonly referred to as humidity. The humidity of the air is an important factor in the comfort level inside the home, as well as outdoors. An unpleasantly low humidity in the home is evidenced, in the inhabitants, by cracked and bleeding noses, dry, raspy throats, and hair standing on end (excessive static electricity).Temperature determines the relative humidity (the actual humidity/maximum possible humidity) for a given volume of air. Higher temperatures sustain the gaseous state of water; consequently warm air can hold more water vapor than cold. As the temperature drops, the physical state of water vapor changes; it liquifies or condenses. The air becomes saturated and reaches its dew point.These facts of physics explain the problems of moisture and condensation in old houses. Condensation occurs on surfaces when moist air is cooled to its dew point. An everyday example is the film of liquid water that appears on the warm side of windows on cold mornings. Another, not so readily visible instance of condensation is the frosty lining of the attic roof boards during a cold Maine winter. An identical situation develops inside the side walls of the old house during the same cold winter.The following is a typical pattern. Each winter of the 150 years that the old house has stood, warm moist air from the living space found its way into the inside space of the side walls. Here, it reached its dew point, condensed on the studs and facing surface of the outside wall, and remained frozen all winter. As spring approached, the outside air warmed up, blew through the drafty wall, and the frost evaporated. Thus, the house survived each season of weathering. However, when insulation is installed in that side wall, condensation becomes a greater hazard. The water vapor now condenses on and within the sponge-like insulating material. Moreover, the insulation impedes the flow of drying breezes. Consequently, the ventilation may not be adequate for the evaporation of the condensed moisture. Thus, side wall insulation may contribute to the emergence of dry rot a fungus that, most probably, had never infected the old house before.The conditions for dry rot's existence are four: 1. moisture; 2. total darkness: ultraviolet light is lethal to the fungus; 3. wood: the fungus eats wood; 4. temperatures above 50F. Prior to the installation of insulating material, ventilation in the side walls was sufficient to eradicate any accumulated moisture before the temperature reached 50F.The complications attending improper installation of any insulating materials are now clear. Dry rot can develop not only in side walls, but also in the attic and foundations. The structure of the old house — the very stability and soundness for which it is prized — falls prey to the fungus.To identify condensation/dry rot problem areas requires an understanding of the ways in which water vapor travels.There are three such methods; each contributes to the flow of warm, moist air from the inside of the house.The first mechanism is diffusion. This is a physical process which happens in the absence of any net transport of air. Molecules move naturally from areas of higher concentration to areas of lower concentration, until equilibrium is established. In the case of water vapor, the molecules of the gas flow towards the outside, to areas of lesser concentration, unless hindered by some type of impermeable barrier. Consequently, this transport mechanism could potentially affect all structural components.The second mechanism, the physical pressure of wind, does involve the net transport of air. This easily detectable phenomenon can be further defined according to prevailing conditions in Maine. During the long winter months in Maine, the wind originates in the north, the northeast, or the north-west 75/o of the time. The net flow of air through the house is from north to south. Cold air from the outside blows through the north wall of the old house, is warmed, and accepts more water vapor as it travels through the house. The warm, moist air reaches the southern wall cavity, where it meets cold, outside air. The relative humidity now becomes intolerable at these low temperatures; excess moisture is left behind as condensation within the side walls. For this reason, moisture and dry rot problems arise most frequently in the south wall of old houses, and least frequently in the north wall.The final mechanism for the movement of water vapor depends on another physical principle the fact that hot air rises. The effect of this process on the old house is greater than one might expect. The actual buoyancy of warm, moist air within the living space exerts a sizeable pressure against the ceilings and roof. Thus, rising water vapor, quickly cooled to dew pointImplied in these latter two mechanisms is a compounding of the previously discussed infiltration problem. The situation in the old house is one of flux in which a variety of physical pressures come into play. The north wind is certainly a considerable force with which to deal, and the buoyancy factor affects the "tightness" of the house.One might well wonder about the emphasis on the condensation problem if these latter two mechanisms the pressure of the north wind and the buoyancy factor actually cause cold air to rush into the old house at such a great rate. Condensation is not a problem when cold air enters from the outside, is simply warmed, and rushes out again. However, one side effect of human habitation and activity within a house is the addition of moisture, of water vapor, to the air. So, to the degree that an infiltration problem exists, a condensation problem also exists. Drafts allow cold air to enter the warm living space. The subsequently warmed air takes on water vapor. The second part of the transport cycle results in the deposit of the excess water vapor as condensation.(top)
Recapitulation of Problem Areas
  • Condition of existing heating system
  • Structure and fabric, examination for heat loss and infiltration
  • Ceiling and attic windows and doors side walls ceiling and attic
    windows and doors
    side walls
    cellar or crawl space
  • Condensation solutions to the above problems may create conditions for dry rot
    • Air flow and water vapor transport mechanisms, effect on structure and fabric
diffusion
physical pressure of wind
buoyancy factor
(top)
4. Solving Insulation Problems in the Old House

The previous section identified several insulation problem areas — some of which the old-house owner may find all too obvious; others require careful analysis. The identification of the problem areas of each old house is the first step towards creating an energy-efficient home. The solutions, the second step, may involve specific insulating technology as well as generally effective modifications of consumption patterns. What follows is a presentation of various strategies to be considered by the old-house owner.(top)

Conservation within the Living Space

The first set of suggestions concerns the control exercised by the inhabitants over the interior environment what can be done within the living space. An old, outmoded heating system is wasteful as well as ineffective. Repair or replacement, requiring professional services, is a high-priority task. Once the heating system is in good working order, the old-house dwellers can make simple adjustments in their habits of energy use, which will have a sizeable impact on both heating bills and long-term conservation. Turning back the thermostat and making up the difference in an extra sweater are everywhere recommended as no-cost, high-return means of reducing energy consumption. Similarly, the frugal use of hot water (i.e. shorter showers, washing clothes in cold water) reduces a significant category of energy use in the home. A corollary of these two conservative mechanisms is the careful avoidance of waste. Windows, doors, And fireplace dampers must not be left needlessly open; water must not run unheeded.

Some important methods of decreasing energy use through control of the interior environment are particularly pertinent to the situation of the old-house owner. Close off the cold, dark, unused rooms in the rambling old house. In the days before central heating, such a winter practice was a necessity. The stove or fireplace became the focus of all essential activity within the home. The modern owner saves on fuel bills while rediscovering something of this core of vitality and community. A more extensive plan for efficient energy use involves the complete orientation of activities within the house, according to the requirements of the enclosure and its siting. Fortunately most old houses were built with the intent of maximizing the benefits of orientation and siting. Again, it is a process of rediscovery. In the winter, the basic principle of following the sun's path around the house should guide the placement of morning, midday, and evening activities.

Beyond these solutions, which call for the adaptability of the inhabitants after an evaluation of recently acquired habits of excessive energy consumption, there are specific "soft technology" methods of reducing heat loss. These solutions do not materially affect the structure of the old house. They stem from a previous era in which the living space was operated efficiently and inexpensively, without dependence on abundant supplies of energy. Shutters, heavy draperies, and window shades prevent heat loss at night and on the cold side of the house, When the sun is shining, they are pulled back to allow the warmth and light full play. Moreover, heavy draperies (portieres) function as draft obstructions. Ceiling fans, especially the old-fashioned ones, are an unobtrusive means of re-circulating heat to floor level. Radiators should be kept clean and should not be painted, as this impedes the transfer of heat. A small fan, stationed near, and aiming at, the radiator maximizes the heat output. Trees, properly set back from the house in consideration of the growth factor, provide shelter beyond the dwelling itself. Deciduous trees, those that lose their leaves in the fall, should be planted on the south and west sides of the house. Here they provide shade and cooling vapors in the warm summer months. Evergreen trees, planted on the north side, protect the house from prevailing winter winds.

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Structural Solutions to the Heat-loss Problem

Implementing conservation measures goes a long way towards creating an energy-efficient home. However, the old house, more often than not, is a loose, drafty structure. Such a building poses many questions to its owner. In most cases the solution suggested above will not suffice to bring the old house up to today's energy-efficiency standards. There are too many structural problems. These problems can be solved with varying degrees of expense and effort; the choice rests with the individual owner. The following discussion sets forth some guidelines for that decision.

As part of the field study effort, Mooney Engineering recommends solutions to the various heat loss and infiltration problems identified. The recommendations stated here take into account the particular problems in old houses. The priority is determined by a measure of cost-effectiveness, defined, in each case, as solutions for which the payback period is 5-10 years or less. The models used to identify problem areas now illustrate the effective solutions.

The percentage on the inside represents the not reduction in heat loss resulting from implementation of the recommendations. As before, the figures on the outside indicate the percentage of total heat loss from each of four vulnerable spots: (clockwise, from the top) ceiling and attic losses, sidewall losses, basement losses, and infiltration through windows and doors. The latter figure is consistently the most significant. In each of the two cases described above (extreme, but not uncommon, situations in old houses), the major portion of the problem is easily remedied. By simply installing storm windows and doors, applying weather stripping, and 12" of fiberglass insulation in the ceiling, the owner of the one-story house reduces the total heat loss by 60%. Identical measures in the two-story house reduce the total heat loss by 55%. These figures imply proper installation and the use of high-quality materials. Furthermore, each of these solutions may be readily accomplished by the owner, without the extra expense of professional services.

This second example illustrates the extent to which basic improvements significantly increase the efficiency of previous attempts to reduce heat loss. The installation of weather stripping and an additional 6" of fiberglass insulation in the attic reduces the total heat loss from each house (with storm windows and doors and minimal attic insulation) by 30%. Today's energy realities call for the extra savings achieved by the additional layer of fiber glass. The importance of careful weather stripping is also evident. Without weather stripping, cold air flows freely between the storm window and the primary window, decreasing the thermal value of the extra layer. Effective weather stripping blocks this flow and maintains a static air mass between the two windows.

The final model also highlights the significant reduction in heat loss attainable with weather stripping alone. After the work has been done (storm windows and doors, insulation in attic and side walls), the addition of weather stripping further reduces the heat loss by a factor of 30% in one case, 35% in the other.

Given the cost-effectiveness and the ease of installation, weather stripping appears to be a critical component of any plan for insulating the old house. However, as in all decisions regarding the well being of the structure, the owner must consider certain cautions. There are several types of weather stripping materials on the market. The felt, adhesive-backed strips are inexpensive but must be replaced each year. Permanent weather stripping, of vinyl, neoprene, or aluminum, presents a greater initial expense but once installed, is not a cause of annual anxiety. Most importantly, the old-house owner must not damage or alter the architectural detail of the structure. Windows and doors are a particularly sensitive area in this respect. As with all introductions of new material to an old house, the addition must be readily removable in the event that it proves obtrusive, or causes unforeseen problems.

Infiltration occurs in areas of the old house besides the windows and doors. The solutions to this draftiness are inexpensive, do-it-yourself tasks. The benefits in terms of energy-efficiency are great, especially in old houses where the processes of aging and deterioration have taken their toll. The following steps are necessary, not only for the reduction of air infiltration, but also for the proper maintenance of the old house.

  • On wood structures, make sure that the exterior paint film is in good condition.
  • On masonry structures, make sure that the mortar is sound. Repoint if necessary. Avoid, however, application of masonry sealers except in highly unusual circumstances. Sealers can trap moisture in masonry walls and cause accelerated deterioration.
  • Caulk all construction joints with a high-quality acrylic or butyl caulk. Fill all holes in exterior wood with putty or glazing compound.
  • Caulk gaps in interior woodwork especially where it butts plaster surfaces and around electrical outlet boxes where necessary. Simple physical inspection, running a hand along the woodwork on a cold winter day, will indicate dramatically where such interior gaps are.
  • Insert strips of felt between wide gaps in floorboards that allow cold drafts. Felt is better than any solid filler because it can expand and contract with the boards.
  • In very old houses, check for gaps where the roof rafters meet the side walls. Large gaps may require stoppage with fitted blocks of wood.

It is not necessary, in fact, it is not at all desirable, to eliminate 100% of air infiltration. Indeed, this would be a virtually impossible task in the old house, which was built to breathe well. Some fresh air is necessary to replace oxygen consumed in normal respiration and combustion. Ensuring adequate ventilation with outside air is also an important element in the solution to the moisture condensation problem.

Before turning to a discussion of the use of insulating materials such as fiberglass batting, shredded cellulose, or foamed plastics, the importance of the aforementioned solutions to the energy-efficiency problem in old houses must be emphasized. Maintaining an efficient heating system, con-serving energy whenever possible, changing wasteful habits, orienting around an energy-efficient lifestyle, rediscovering "soft technology", and carefully utilizing unobtrusive means of reducing infiltration are the first steps that the old-house owner must take. With regard to cost-effectiveness, potential benefit in energy savings, and preserving the architectural integrity of the old house, these solutions are top priority.

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Installing Insulation

Fiberglass, cellulose, and foamed plastics are commonly installed in three places in the home: the attic, the basement or crawl space, and the sidewalls. As identified in the field study analysis, heat loss through the ceiling is a major portion of total heat loss. Thus, attic insulation, properly installed, is a feasible choice for the old-house owner, that will undoubtedly result in energy savings. Moreover, attic insulation is an unobtrusive addition, easily owner-installed. Similarly, insulation in the basement or crawl space is an effective possibility for the old house. In each case, the insulation impedes in-filtration from drafty foundations and through floors. Both attic and basement/crawl space solutions require that the owner understand the nature of the problem as well as the complete remedial process. As always, the old-house owner must exercise extreme caution and care when applying these new materials to an irreplaceable structure.

Sidewall insulation is the last resort for the old house. Implementation of other energy-conserving measures relegates this drastic step to a low-priority position; the relative savings of energy and money become inconsequential. As proper installation of side wall insulation requires prior application of a vapor barrier and, consequently, the gutting of the interior wall, the old-house owner concerned for the structural character of the house will recognize that the benefits may not outweigh the costs. Furthermore, in the case of sidewall insulation, as opposed to attic, basement, or crawl space solutions, the installation is irrevocable; if complications arise, there is no second chance.(top)

Eliminating the Moisture Condensation Problem

As indicated previously, the condensation/dry rot problem begins with the installation of insulating materials. This is a major factor in the determination of priorities for achieving energy-efficiency in the old house. If such a state can be reached without interfering with structural materials so much the better. However, when insulation is necessary, there are simple procedures, which eliminate the threat of dry rot.

The installation of a vapor barrier is the critical safeguard. A vapor barrier is an impermeable membrane, which blocks moisture flow. Aluminum foil or 4-6 mil polyethylene sheeting are the vapor barriers most commonly coupled with insulation installation. The vapor barrier must be placed on the warm side of the insulation, otherwise it is counter-effective. To prevent dry rot within the structural spaces filled with insulation, it is essential that warm, moist air from the living space never reach the cavity where it cools, condenses, and is absorbed by the insulating material. Proper and effective application of insulating materials requires the prior installation of e continuous and unbroken vapor barrier. In old houses, this is easily done in attics, basements, and crawl spaces. However, it is virtually impossible to install an adequate vapor barrier in the sidewalls without gutting the interior wall or adding a new layer, made up of the vapor barrier and the insulating material, to the existing interior wall surface. Each of these solutions radically alters the distinguishing architectural details and historic features of the structure. Consequently, attic, basement, and crawl space insulation take precedence over sidewall remedies.

A further caution regarding vapor barriers applies to the addition of a supplementary layer of insulation. Assuming proper installation of the original layer, complete with vapor barrier on the warm side, the second layer is laid directly over the first, with no vapor barrier between the two. Particular care must be taken to remove the aluminum facings when layering fiberglass blanket or batt insulation.

Vapor barriers on the interior wall surface also effectively impede moisture flow into the wall cavity. Some materials for this purpose are aluminum paint, glossy, oil-base paints, and vinyl wallpaper. Each of these presents a problem in terms of compatibility with the old house fabric and materials. The old-house owner must weigh the potential benefits against such considerations.

For the old-house owner who is concerned about this question of compatibility, as well as for all concerned with the structural stability of their homes, there are ways of reducing the moisture content of the air procedures which reduce the need for vapor barriers, such as impermeable paints and vinyl wallpaper, on the interior wall. Eliminating the sources of water vapor and ensuring adequate ventilation are important solutions, in conjunction with the vapor barrier on the warm side of the insulation, to the condensation/dry rot problem.

  • The critical sources of water vapor are readily controlled:
    A basement may have standing puddles or damp soil (clay or bedrock). Either situation is a primary cause of excessive water vapor within the living space. Proper grading, gutters, and downspouts rectify any reverse drainage problems.
  • Laying a new floor surface, consisting of a gravel base, a properly sealed vapor harrier ( 6 mil polyethylene sheet), and topped off with a concrete slab, stone, or other protective material, prevents the intrusion of this subterranean moisture. Similarly, a properly sealed and ventilated vapor barrier should cover the ground of a crawl space.
  • Ventilation of bathrooms, kitchens, and laundry rooms is another important step toward reducing moisture in the home.Cooking with the lids on pots reduces not only the amount of escaping water vapor but also the cooking time.
  • Most houseplants are responsible for a sizeable portion of the water vapor in the air. Consider a separate greenhouse or fewer plants, perhaps a variety that requires little water.
  • Drying laundry or wood inside the house has the same effect. Avoid this practice whenever possible.
  • Humidifiers should be turned off at any sign of excessive moisture build-up, i.e. the appearance of water or frost on the warm side of the inside pane of glass of windows equipped with storm sash or insulation gloss.
Adequate ventilation, allowing for a controlled source of infiltration, is a necessary adjunct to the installation of vapor barriers and insulation in the old house. Cold, dry outside air dilutes the warm moist, inside air. In the old house, vents in both the basement and attic ensure the elimination of the excess moisture that inevitably bypasses barriers of all kinds. Overall, the old house breathes well; cold-side venting in side walls is not a major concern. However, the old-house owner must take care not to counter-act this structural advantage by encasing the house in aluminum or vinyl siding or applying on impermeable layer of aluminum foil under that siding, essentially installing vapor barriers on the wrong end of the problem.(top)

5. Conclusion

Insulating the old house is an undertaking that involves more than a concern for energy-efficiency. In the name of energy- efficiency, irreparable damage can be done to the frame and fabric of on old structure. The insulating materials and methods have not been sufficiently tested to warrant their indiscriminate use within such valuable resources as old houses. Consequently, the preceding pages have emphasized a cautious approach to the problems of heat loss and moisture condensation an approach which promotes old-house values, the specific built-in advantages of the structure, as well as the adaptation of the inhabitants according to the optimum energy-conscious use of their home. If the initial conservative steps revolve around existing conditions, the old-house owner avoids the additional complications surrounding the radical introduction of new materials. The fact that old houses are irreplaceable resources underlies the need for caution. The care that the old-house owner takes in determining the answer to the energy-efficiency problem engenders an appreciation of architectural and historic details, the weathered soundness of the house end the pragmatism of the original builders. This practical sense has re-emerged in the post-industrial age. It is evidenced in the recycling of old structures. Energy-efficiency is a critical component of the recycling effort; the present era of limitation and conservation so demands. Yet this need not be a restrictive age. In the old house, one discovers the opportunity for a resourceful and vital approach to the future.

The conflict between preservation and renovation is boldly depicted in a short story by Herman Melville entitled I and My Chimney.

I and my chimney, two gray-headed old smokers, reside in the country. We are, I may say, old settlers here; particularly my old chimney, which settles more and more every day.... It need hardly be said that the walls of my house are entirely free from fireplaces. These all congregate in the middle in the one grand central chimney, upon all four sides of which are hearths two tiers of hearths so that when, in the various chambers, my family and guests are warming themselves of a cold winter's night, then, though at the time they may not be thinking so, all their faces mutually look towards each other, yea, all their feet point to one center; and, when they go to sleep in their beds, they all sleep around one warm chimney, like so many Iroquois Indians, in the woods, round their one heap of embers.

[His wife calls in a master-mason (described by the narrator as "a rough sort of architect") who presents elaborate proposals for removing the chimney, all of which are stoutly resisted. The narrator rumbles on to conclude:]

What narrow escapes have been ours! Once I found in a drawer a whole portfolio of plans and estimates.

Another time. upon returning from a day's absence, I discovered my wife standing before the chimney in earnest conversation with a person whom 1 recognized as a meddlesome architectural reformer who, because he had no gift for putting up anything, was ever intent upon pulling down; in various parts of the country having prevailed upon half-witted old folks to destroy their old-fashioned houses, particularly the chimneys. But worst of all was the time I unexpectedly returned at early morning from a visit to the city, and upon approaching the house, narrowly escaped three brickbats which fell, from high aloft, at my feet. Glancing up, what was my horror to see three savages, in blue jean overalls, in the very act of commencing the long-threatened attack. Aye, indeed, thinking of those three brickbats, I and my chimney have had narrow escapes. It is now some seven years since I have stirred from home. My city friends all wonder why I don't come to see them, as in former times. They think I am getting sour and unsocial. Some say that I have become a sort of mossy old misanthrope, while all the time the fact is, I am simply standing guard over my mossy old chimney; for it is resolved between me and my chimney, that I and my chimney will never surrender.(top)