Publisher’s version / Version de l'éditeur:
Home Builder Magazine, July/Aug., p. 23, 48, 1990-07
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Design and construction solutions to problems with indoor swimming
pools
Rousseau, M. Z.
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De sign a nd c onst ruc t ion solut ions t o proble m s w it h indoor sw im m ing
pools
N R C C - 3 4 9 8 7
R o u s s e a u , M . Z .
J u l y 1 9 9 0
A version of this document is published in / Une version de ce document se trouve dans:
Home Builder Magazine, July/Aug., pp. 23, 48, July, 1990
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Home BUILDER July/Aug, '90 23
board demonstrated quite low permeability to air, simi-lar to foil-back gypsum board.
Gypsum board products can also function as air bar-rier materials, However, they are usually not recom· mended for areas of sustained high humidity such as swimming pools, unless the design of the assembly pro-vides sufficient protection against moisture absorption (check with gypsum-board manufacturers). Neverthe· less, a foil-back gypsum board or foil-back water-resist· ant board with the foil facing the inside could be used on the warm side of the wall or roof assembly.
Making the Structure Airtight
To obtain an airtight assembly over the enclosure, connect wall or roof air barrier materials to other air barrier materials in floors, windows and skylights and seal the joints with sealants, adhesive membranes or gaskets. For increased rigidity of the joints, support the adhesive membranes and tapes and mechanically clamp them to the substrates, unless testing indicates that the membrane adhesion to the substrates is alone sufficient to sustain the pressure differentials expected in the building,
As well, openings through the airtight material must be designed and builtｾｯ be airtight and structural. Build rigid airtight･ｮ｣ｬｯｳｵｲ･ｾ around light fixtures and seal them to the other components of the air barrier system, Recessed light fixtures must be designed for installation into insulated ceilings. Check with your local building authority for code reqUirements.
When an indoor pool is being added to an existing house that is not airtight, build the pool enclosure as a sepa.rate, airtight compartment. This configuration ensures that the high moisture content of the pool air is managed at source and has no accesstothe house's leakier walls and roof, The partition wall between the pool area and the house must be as airtight as the enclo· sure's exterior walls and roof so the air barrier system remains continuous, As well, keep the forced-air heat-ing and distribution systems for the pool separate from that for the rest of the house.
Ventilation cannot make up for a pool enclosure that leaks air. However, in an airtight enclosure, mechanical ventilation can be set up to slightly depressurize the pool enclosure. This arrangement ensures that small (unavoidable) gaps in the air barrier system will induce some cold air infiltration, rather than warm, humid air exfiltration.
Schematic of a vertical section of a house with an attached swimming pool
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Design and construction flaws in the enclosing walls and roofs of residential indoor swimming pools increase the risk of building materials being damaged by concealed condensation in winter. In this issue, we look at how to avoid some of these common problems. Damage to indoor pool enclosures are severe in mag-nitude, difficult to investigate and expenSivetorepair. They also develop qUickly. Evidence of roof or wall flaws includes condensate water dripping from ceiling light fixtures or interior finishes, These visible prob-lems warn of concealed damage such as rotting exterior sheathing and structural members and wet insulation in roof or wall cavities,
Because an indoor pool space operates under condi-tions ofhigh humidity (24-2 6 degree and 40 to 80% rel-ative humidity), it is more vulnerable to condensation problems than low-humidity environments, In particu-lar, cracks, ioiots and holes left between materials allow moist indoor air to escape into cold areas of walls and roofs and deposit moisture there, The design and con-struction of pool enclosures according to building sci-ence principles are ofutmost importance.
Design and construct an airtight assembly, or air bar-rier system, to control concealed condensation, Select materials with low permeability to air as well as rigidity and structural strength to sustain wind loads, For the air barrier system to work, joints between these materials as well as interfaces with other components (such as light fixture openings) must also be airtight, rigid and structural, In addition, install a vapour barrier on the warm side of the enclosure to control moisture diffu-sion, aless significant mechanism ofmoisture transport than air leakage, but one not to be ignored in high-humidity places,
Sheet material made of a cement-base core with water-resistant facings can function as an air barrier material and Is suitable for swimming pool applica-tions. In aseries of tests contracted by CMHC, acement
Design find Conslruelion Solutions
to
Problems
With Indoor Swimming Pools
Final Points
toRemember
In conclusion, here are some additional points to ... ＭＭＭＧｾ consider for installing indoor swimming pools: ｾ
•••
"Ventilation cannot make
up for a p091 enclosure
that leaks air."
•
Madeleine Rousseau, Architect, National Research Council.
Madeleine Rousseau is an architect in the Technical tn/ormation Group at the National Research Council's institute/or Research in Construction,
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3% 1% 1% 1% 0.5% 0.5%2211-Marketing
_
grams such as new homes month and model home courts and parades where joint efforts work well.
5. Train sales representatives to "discover new home motivators" and to "breed discontent."
Your on-site sales staffmust uncover exactly what the sales office traffic is looking for in anew home, Develop a presentation that accentuates the reasons why new home prospects want to move.
Why do people want to move into a new home? Per-haps they wish to improve their life-style, enhance their financial security, or live in a new neighbourhood with all the amenities. Attack with a presentation that emphasizes new home motivators and breeds discon-tent by focusing the prospect on what they would like changed about their present home.
Market share is not bought, it is earned, We face a housing economy in which the consumer asking and we must interpret the mixed messages the consumer is sending. Concentrate on new designs that suit can· sumer needs, create financial packages for the "save-save" mentalities of the new decade, build a quality product and market creatively and aggressively.
The business of building residential communities involves risks that are far too large to avoid paying allen-tion to every detail. Plan carefully, monitor the market regularly and update your marketing strategies on a continuing basis,
In a rough market, don't JUSt shrink the budget. Attack and succeed, with guerilla marketing! HI
23"-'Iechnology
_
• Pool enclosures should not be built to "breathe" like older houses, Older houses operated under very low indoor humidity levels;
• Expensive mechanical eqUipment does not coritrol concealed condensation. This equipment conditions the indoor climate but the enclosure still has to effec-tiveley separate indoor and outdoor climates; • Avapour barrier alone will not control condensa-tion. Avapour barrier only reduces moisture diffusion to an inoffensive amount. It is necessary, but not suffic-ient, to control condensation, An air barrier system tackles the major transfer of moisture into cavities that takes place through air flow, and:
• Condensation in roof spaces is not due to lack of roof ventilation. In fact, installing more vents can cause the air pressure in the roof space to drop and encourage moist indoor airtoenter through ceiling leaks, increas-ing the condensate in the roof cavity. However, in the spring, ventilate wet roof sheathing and framing to dry them before applying a permanent solution to conden-sation problems.
For more information about the material in this column refpr to: Building Science Insight '86, Ｇｾｮ Air Barrierfor the Building Envelope"(24pages, 110), or Building Practice Note No. 54, "The Difference Between a Vapour Barrier and an Air Barrier" (13 pages, free), 1b order, make cheques payable to the Receiver General and forward to Publications Sales, NRC, Montreal Road, Ottawa, Ontario, KIAOR6, I-B
CMHCnSCHL
Helping to house Canadians
Canadian Housing
Information Centre (CHIC)
.6.
Audio-Visual Malelials
For more information on the above and other services please contact The Manager, Canadian Housing Infor-matian Centre, Canada Mortgage and Housing Corpo-ration,682Montreal Rd.,Ottawa, K1 A OP7(telephC2oe
613-748-2362.fax 613-748-6192).
Canada
Circle No.1 06 on Inquiry Cord.
48 Home BUILDER July/Aug, '90
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