When it comes to saving money associated with heating and cooling, air movement, between the outside and inside the structure is the source of most energy loss. Stopping air movement is critical and is the “low hanging fruit on the energy savings tree”.
Most homes we inspect use fiberglass or cellulose insulation bats on the floor of the attic. This type of construction requires attic venting which provides a free flow of air from the attic to the outside. Making matters worse, bat insulation is not good at stopping air flow at penetrations in the attic floor where electrical, plumbing and HVAC lines are going through the attic floor to the living space below. So there’s a flow of conditioned air from the living space, through the attic, and then to the exterior of the home through the attic venting system. Therefore, there is a substantial heating/cooling loss from inside your home through the attic and to the exterior of the home. And obviously, we all pay dearly for energy to keep the house warm or cool depending on the season.
These days, many homes utilize spray foam as an insulation material which is typically applied directly to the underside of the roof and doesn’t require attic vents. All the nooks and crannies are sealed with the spray foam and as result, air movement, from inside the home to the outside is pretty much stopped, providing a substantial savings.
Some people have inquired about the impact of spray foam insulation and the possibility of indoor air quality issues due to a lack of fresh air. It’s an excellent question!
Spray foam insulation provides such a good “air block” that if the entire house is insulated with spray foam it could cause a problem with indoor air quality (IAQ), and mechanical ventilation may be needed due to a lack of fresh air. There are lots of different systems that can introduce fresh air, some of them are energy efficient. Energy recovery ventilator (ERV) systems provide a controllable amount of fresh air in the structure and are energy efficient. In an older house there is probably enough air leakage through the walls, windows, doors, and other openings that more than likely there’s enough natural ventilation in the structure without adding a mechanical ventilation system even if the attic is insulated with spray foam.
So, in our opinion, spray foam insulation applied to the underside of the roof is the best way to go with insulation. And by the way, while you’re at it, it pays to seal any air gaps in the basement perimeter walls especially at the top of the foundation where it meets the wood framing. If you decide to explore the installation of spray foam, keep indoor air quality in mind. A good AC contractor or spray foam installer should be able to help guide you with this concern.
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