Thread: hatch insulation

Nine times out of ten, when there's a piece of insulation for the attic hatch, it's not in place when I open the hatch. I'm sure you find them this way too.

Do you leave it the way you found it or put it back in place when you leave the attic? If you leave it the way you found it, do you write it up?

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Originally Posted by John Dirks Jr

Nine times out of ten, when there's a piece of insulation for the attic hatch, it's not in place when I open the hatch. I'm sure you find them this way too.

Do you leave it the way you found it or put it back in place when you leave the attic? If you leave it the way you found it, do you write it up?

I leave it the way I found it and write it up. If I put it back it will fall off the next time the hatch is opened. Needs to be attached!

I put it back and then crawl out a roof vent

The first illustration from AD shows gaps in the insulation at the sides of the box.

The second version does not maintain integrity with the sidewalls of the well.

The third version is closer to what I recommend and have done. It should be of suffiicient rigid foam to meet the ceiling R requirement plus have a double gasket system: one weatherstrip where the hatch lays on the casing at the ceiling then a second near the top to trap air along the sides of the hatch. This does two things: meet the R value required and meet the air tightness also required of the structure. Note that if the combined weight of the hatch is insufficient to compress the lower weatherstripping, you need to glue a brick or some similar weight on top. a snug fitting piece of 1/2" drywall provides weight and carries a lower flame spread rating than unprotected foamboard. This not only compresses the lower weatherstripping but prevents the hatch from flipping open during sudden severe pressure gradients as seen when a door slams or doing severe weather. I find single 1/4" plywood lids cocked open all the time. The joint btw the ceiling drywall and framing for the hatch should be caulked. I use a UL 181 duct sealing mastic but regular acrylic latex painter's caulk will suffice. I use this to seal all ceiling penetrations including light fixtures, electrical cables, plumbing stacks, etc. 'Can'-type ceiling lights are now replaced with ICAT fixtures--no insulated boxes, which inspite of the illustration in the IRC, are a fire hazard for non-IC fixtures.

For disappearing stairs, you can buy the expensive insulated brands such as Rainbow but they probably won't meet your total R requirement so they need a supplemental lid.

These hatches are a huge problem. They not only lead to huge amts of wasted energy but can be a safety problem. Placing a large exfiltration point at the top of the thermal envelope can, by itself, lead to backdrafting, esp. water heaters and open hearth fireplaces. They can also provide easy entrance points into the home for bugs such as cluster flies. During a house fire, it would tend to ventilate the upstairs hallway but could allow the fire to quickly spread across the rest of the home. In homes with fire sprinklers, it would tend to defeat any heads nearby from actuating.

This is an area gettting much attention because it is a major reason for failing blower door tests and energy rating. The fire issue will become a greater issue now that fire sprinklers are required by the IRC for new construction.

Thanks, Bob, for that post - lots of stuff to chew on there.

Originally Posted by A.D. Miller

It needs to be gasketed and properly insulated to the same R-value as the surrounding ceiling as per the IEEC.

Thanks for that third pic AD. That is how I write up all hatches. Pull down stairs differ some what but on the same line.

Don't forget vertical kneewall hatches through the thermal envelope. The kneewall needs to be insulated under the plate as well. People love cutting these hatches into the unconditioned attic right off bedrooms then wonder why their energy bills are so high. These really should have insulated exterior doors but it's kinda hard to cut some down. Since it is technically not a 'door' designed for foot traffic per se, it really should meet the sidewall weatherization requirements including air sealing and R value.

Is the third version/pic you guys referring to the image in the second 750 x 600 attachment or was their another attachment that has now been removed? Thanks...I want to make sure I'm looking at the correct details.

Thank you for posting the images.