Foam Insulation for Attic Spaces

Spray Polyurethane Foam Insulation can be used in two common ways to insulate your attic space and protect your home from weather and other moisture related damages.

The method of use for spray foam in the attic is often dictated by the building science and design principles your architect and/or builder subscribes to. In a traditional vented attic, insulation is used on the attic floor to insulate the ceiling from the seasonal heat and/or cold. Spray foam is used where traditional fiberglass batts, or cellulose is used; between the floor joists. The rest if the attic is left un-insulated and highly vented through gable, soffit, and ridge vents in the roof structure. This type of engineered system is the most common throughout the US, but may not be the most effective.

In this application, considered the most effective by most of the SPF industry, the foam is sprayed directly to the underside of the roof between the joists, down around the rim and into the soffit areas, on the gable wall ends; effectively sealing off and insulating the entire attic space from any air infiltration.

The traditional practice of insulating the underside of the roof in the attic has raised much debate in the building industry because "standard" roofing and design techniques call for the attic to be ventilated in order to reduce moisture problems and heat build-up in the hot summer months.

However, in a vented attic situation it will become approximately 130-degrees in the summer. There's no reason for your air-conditioning and vent-ductwork to have to work in that type of severe conditions. There is also opportunity for moisture to form due to condensation on these appliances.

By applying spray foam directly to the underside of the roof deck, it now insulates the attic space from the extreme heat that once radiated through the hot shingles, sheathing, and roof. The severe temperatures no longer exist in the attic. In short, the attic now becomes a "conditioned" space of the house that is just as comfortable as any other room in the home.  Most builders and designers will tell you that this system is no good because wood needs to breathe and that the shingles on your roof will now overheat, get too hot and curl off.

There has been a great deal of research on the "breathing wood" issue and it has been found that most furniture manufactures actually kiln dry wood before use. They claim that if any wood is permitted to "breathe" this adds to deterioration over time. Kiln dry wood, used in all furniture, contains a small amount of moisture. If that moisture continues to dry out you will start to see cracks and splits. They take extra precautions to make sure that wood is sealed completely. Wood must be totally sealed. Properly finished and maintained furniture will not have this problem. Perhaps this is why we paint our house, and our fences, and everything else. I know someone who put up a fence a few years ago, left it to breathe, and now it is falling down because it is rotten. So much for breathing wood…

ELK Premium Building Products claim that their shingles have no problems whatsoever being used over an un-vented roof deck. So much for curling shingles…

A roof system insulated with spray foam reduces energy several ways. Energy loss from ducts located in the attic is essentially eliminated. The top of the building is much tighter resulting in less infiltration and exfiltration, so excess moisture isn't pulled into the attic. Infiltration through the ceiling is also reduced. In addition, the attic temperature is lower, which further reduces energy loads.

In a standard insulation system, ceiling insulation reduces the transfer of heat from the attic to the living space (in the summer). Attic temperatures can often approach 140F during the day. Most of this heat enters the attic space through a multi-step process. First, solar energy warms the shingles and sheathing. The hot sheathing then transfers heat to the rest of the attic through conduction, convection and radiant heat transfer. The 140F temperature of the underside roof surface drives the heat transfer process.

By insulating the roof surface with spray foam, the surface temperature exposed to the attic (the temperature driving the heat transfer) is reduced. Both conduction and convection heat transfer are proportional to a temperature difference, so that heat transfer will be reduced proportional to a drop in surface temperature. This area will now be close to the same temperature as the living area of your home.

• Duct leakage and heat loss/gain from ducts is much less of an issue.
• Air sealing is easier in the roof than in the ceiling.
• Dust and loose insulation are less likely to migrate down to the living space.
• Tests show energy costs are lower when the attic is sealed.

Further information is available from ASHRAE (8700-527-4723) in a publication titled "Vented and Sealed Attics in Hot Climates".

Foam Insulation for Crawl Spaces

How many times have you seen round/oval vents penetrating from the crawl space into the house through rectangular holes? This situation is cause for great concern. We already know that fiberglass batts cannot control or prevent air/moisture movement and infiltration. That being the case, even if your crawl space is "properly" insulated with batts, they will not prevent cold air, warm air, or contaminated air from entering the living space of your home.

If the crawl space in your home is not fully sealed from your home, there is a strong likelihood that contaminated air, earth gases, mold, rodents, and more can penetrate your living space.
Spray foam insulation installed between the floor joists in your crawl space is the only material that will create an effective thermal barrier from obstructions such as wiring and plumbing, ductwork, and narrow or wide joist spacing.

Batts are often compressed during installation due to the use of wire insulation hangers. Open web floor trusses create additional problems in that the open webs create pathways for air to move around the batts.
During the summer, warm humid air can flow around the batts and create condensation, mold and decay problems in the floor system. Open web floor trusses are virtually impossible to adequately insulate with batts.
Spray foam circumvents floor insulation problems through its ability to completely fill voids and open spaces. Areas around wiring and plumbing as well as open webs of floor trusses can be completely filled, resulting in a complete, essentially uniform thermal barrier on the floor. Spray foam insulation in the crawl space is a superior insulation product that overcomes several disadvantages of other insulation products. Spray foam can provide a more uniform, consistent thermal barrier as well as provide stack effect / air flow retarding functions.

Closed-cell spray foam will also serve as an effective moisture barrier between the ground and homes subfloor surface. It will also prevent "stack effect" air/moisture movement into the homes walls and upward into the homes attic space, which can cause even more problems. Queen City Foam and Coatings is also able to provide a closed crawl space using the Crawl Space Care system. Please ask us about this service.