Techniques > Energy Conservation
More layout tweaking needed.
Insulating of Old Houses
- The Old House and Energy-Efficiency: A Perspective
- Insulation Problem Areas in the Old-House
- Heating Requirements and the Old-house structure
- Moisture condensation in old houses
- Recapulation of problem area
- Solving Insulation Problems in the Old House
- Conservation within the living space
- Structual solutions to the heat loss problem
- Instaling insulation
- Eliminating the moisture condensation problem
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.
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.
3. Insulation Problem Areas in the Old 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.
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.
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
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.
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),
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.
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.
- attic/ceiling loss
- wall loss
- basement/floor loss
- direct window and infiltration loss
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 40ºF, 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.
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
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 50ºF. Prior to the installation
of insulating material, ventilation in the side walls was sufficient
to eradicate any accumulated moisture before the temperature reached
50ºF.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 75º/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.
Recapitulation of Problem Areas
- Condition of existing
and fabric, examination for heat loss and infiltration
- Ceiling and attic windows and doors side walls c
eiling and attic cellar or crawl space
windows and doors
solutions to the above problems may create conditions for dry rot
- Air flow and water
vapor transport mechanisms, effect on structure and fabric
4. Solving Insulation Problems in the Old House
physical pressure of wind
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.
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
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
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.
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.
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.
all construction joints with a high-quality acrylic or butyl
caulk. Fill all holes in exterior wood with putty or glazing
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.
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.
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
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.
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:
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.
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.
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.
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.
laundry or wood inside the house has the same effect. Avoid
this practice whenever possible.
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.
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
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)