Insulating the foundations of existing houses
07th June 2023
What does foundation insulation amount to? Many people wonder whether there is any point in going to extreme lengths to install foundation insulation after their house has been built.
But the rationale behind insulating your home from the ground up, even if it is an old home, is compelling. The lack of an insulated foundation in homes can result in heat loss, mould, condensation, thermal shock, surface floods, radon gas infiltration and rotting walls. Homes with a basement design that takes this into account tend to be free from these issues, while retrofitting foundations can improve a property with state-of-the-art technology, as well as awareness.
For years, people have managed to ignore the great energy efficiency potential of foundation insulation. Professionally installed insulation is estimated to reduce heat loss by a minimum of 50 percent, with a similar impact on energy bills. What’s more, it improves the ambiance of below-grade rooms, and combats mould growth in homes. According to the experts at Ecofriend, adding insulation to foundations, basements and crawl spaces can make a big difference to existing homes and their energy efficiency.
Insulating basement exterior walls
This minimises thermal bridging and reduces heat loss across the foundation. It prevents moisture intrusion because installing insulation in the basement exterior walls acts like a capillary break that stops moisture from entering. This is especially important in freeze-thaw cycles. Moreover, exterior insulation reduces condensation as well. Even though insulating exterior walls is expensive, especially if you do it on an existing building, it will prove well worth it in the long run.
Insulating interior basement walls
This is less expensive than insulating exterior walls, mostly because the choice of materials and skilled professionals is bigger. You are able to choose from a wide assortment of insulation options when determining which material gives the best results for the price. Be prepared to lose a few inches of space.
An added consideration is existing damp-proofing; where exterior insulation will always protect your damp proofing, interior insulation does not necessarily do this. The experts at Ecofriend say that moisture weeping takes place throughout the foundation walls if the perimeter drainage is poor and the interior insulation gets saturated. Another issue is the gases that some forms of insulation release. They recommend covering any interior insulation with a fire-coated covering if the material releases any toxic compounds.
Insulating crawl spaces
Before you get to grips with the crawl spaces underneath your home, you need to consider whether you will vent the area or not. If you decide to vent it, you need to make sure all holes in the floor are sealed, so that no outside air will end up making its way into your house. Make sure seam are sealed well so the insulation is not affected by outside air blowing in. Over a dirt floor, you can use polyethylene vapor retarder or equivalent materials. Note that polyethylene easily gets damaged and that to prevent this you need to cover it with sand or a thin concrete slab.
If you decide to leave the crawl space unvented, simply check holes in the foundation from where air could enter and use the plastic ground cover. Pull this up to the wall and secure it to the mudsill before installing rigid insulation foam board from the foundation’s subfloor to the floor of the crawl space (usually a concrete slab).