Video answer · Seal Tech Insulation
What Is the Best Attic Insulation for a Michigan Home With High Energy Bills?
The best approach is to air seal the attic completely and then install insulation up to the right thickness.
The short answer
The best approach is to air seal the attic completely and then install insulation up to the right thickness. Spray foam is the most thorough way to air seal. For many open attic floors, sealing the bypasses and adding blown-in insulation to full depth is also very effective.
What the crew says in the video
- The crew recommends spray foam to completely air seal the house.
- Then insulation goes in to full thickness to stop as much heat transfer as possible.
The best attic insulation: seal first, then insulate
Heat moves fastest through air. If warm air is escaping through gaps around lights, fans, and chases, adding more insulation on top only helps so much. Sealing those gaps first is what makes the insulation perform.
How much insulation?
Most of Southeast Michigan is in Climate Zone 5. Energy codes there call for high attic R-values, commonly R-49 or more for new work. Many older attics have a fraction of that. Getting the whole attic to an even, full depth matters as much as the total.
Spray foam vs. blown-in
| Approach | Best for |
|---|---|
| Spray foam on the roofline | Attics with ductwork or equipment, cathedral ceilings, knee walls, finished or storage attics |
| Air sealing + blown-in on the floor | Open, accessible attic floors with good ventilation |
| Spray foam air seal + blown-in | Getting both the air seal and the depth at a good value |
Further reading: Adding Insulation to an Existing Home (U.S. Department of Energy).
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