Energy Efficiency and Modern Homes

Energy Efficiency and Modern Homes

Modern homes, constructed with significant advancements in building products, techniques, and the development of high-performance heating, cooling, and other appliances, are significantly more energy-efficient than their predecessors. Yet the advantages of foundation insulation tends to be neglected. An uninsulated, conditioned basement might contribute to as much as 50% of a tightly sealed, well-insulated home’s total heat loss. Foundation insulation chiefly aims at reducing heating costs without significantly affecting cooling costs. It enhances comfort, curbs condensation thereby mitigating mold growth, and improves the habitability of below-grade rooms.

Types of Foundations

The primary types of foundations include full basement, slab-on-grade, and crawlspace. Factors such as deep frost lines and low water tables often make full basements the preferred choice. Alternatively, slab-on-grade with walkout basement construction is also common, and home additions usually feature crawlspace foundations.

Full Basements

Basements can be insulated using both interior and exterior measures. The interior insulation approach employs traditional 2×4 framing with batt or wet-spray insulation. If the batt insulation’s vapor retarder isn’t fire-rated, drywall should cover it. Rigid foam can also serve as interior insulation, held in place with furring strips. Most foam insulation boards should be covered with drywall as per fire codes.


Exterior foam and foam-form insulation systems can effectively insulate crawlspace walls. If foam insulation is employed, it should extend from the foundation top to the footing top. Insulation measures should ensure proper ventilation to control moisture levels.


Insulation is crucial for slab-on-grade construction to reduce heating costs and mitigate cold-floor syndrome. Insulation should extend from the slab top to the footing top.


The cost of insulating a full-basement foundation varies. Considering a figure of $1,200 added to the mortgage of a new home would result in an annual increase of $106 for a 30-year, 8% loan. Thus, the total heating and mortgage costs would be comparable, but the house would be more comfortable and healthier.

Frequently Asked Questions

Q: Should a basement that is unfinished also have foundation insulation?
Unless the above floor is insulated, yes. The basement forms part of the house’s complete thermal structure.

Q: Can floor insulation above a basement / crawlspace replace foundation insulation?
Yes, but this arrangement would require insulation around any pipes, ducts, and HVAC equipment in the basement to prevent freezing.

Q: Does exterior insulation improve energy performance?
For a basement designed with passive solar design and substantial south-facing windows, exterior insulation could be beneficial. Otherwise, the energy savings are minimal.

Q: Is it recommended to have vapor barriers inside foundation walls?
Yes, if interior insulation is used.

Q: Does foundation insulation increase termite risk?
No. The infestation risk exists regardless of foundation insulation. However, exterior insulation could complicate termite detection and treatment.

Q: How long does exterior foundation insulation last?
When correctly installed, it should last as long as insulation installed in other parts of the building.

Q: Is it necessary to protect the foam insulation above grade?
Yes. Sun and physical damage can degrade foam considerably, so it should be protected.

Q: Does foundation insulation increase radon risk?
No. In fact, foundation insulation may help reduce radon entry by minimizing thermal stresses, which in turn reduces foundation cracking.

Q: Should crawlspaces be ventilated?
It’s preferred to install a vapor barrier and close operable vents. If local codes require ventilation, use insulation on the floor incorporating a vapor barrier.

Q: Are insulating concrete form (ICF) systems cheaper than an insulated, poured-in-place concrete wall?
The costs are project-specific. However, ICFs are generally competitive.


In conclusion, a carefully planned insulation system can lead to significant energy savings in the long run.

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