Summer heat getting to you? Power Bills climbing? Feel like there must be a hole in your house letting in all that Hot Air? Most likely there is, and many homes have more than one. Those pesky pull down attic stairs, hatches or doors. These small access points can have a huge impact on your comfort and bills.
Let’s assume you have a well insulated attic per our local codes at R-30. We’ll ignore framing, HVAC equipment, and storage areas for now and just say the whole attic is R-30. The problem is heat flows thru the path of least resistance (by the way that’s what the ‘R’ in ‘R-value’ stands for). Heat in your attic is like water in an aquarium, drill a small hole in the aquarium and the water WILL drain out even though 99% of the glass is in good condition. Have a spot with little to no insulation and heat will flow thru.
Bear with me for this section of math. Let’s say your attic is 1,000 ft² and your pull down attic stairs are 5 ft by 2 ft for 10 ft². In this example the attic stairs are 1% of the area, 10 ÷ 1,000 = 0.01 or 1%. To calculate the average R-value of the attic we have to use the U value of each section, which is the inverse of the R-values.
1/30=0.0333 = U value of insulated area of attic
1/1=1.0 (assuming the attic stairs has an R-value of 1, actually much less)
0.03333 × 99% + 1.0 × 1% = 0.04297 = Total attic U value
1 ÷ 0.04297 = 23.27 = Total attic R-Value
This means for that one attic door you’ve lost 23% of your attic R-Value, from R-30 to R-23. Then if you combine that with the poor air seals typically found on these doors you are effectively putting as much heat in the house in that one spot as you are across your whole attic.
There are plenty of solutions out there, below are some pictures of some.
But there are some key elements you want to consider:
- R-Value at least a third of the attic R-value, R-10 for an R-30 Attic. In this example you’d raise your attic R-value to R-29 from R-23.
- Provides a good air seal between attic and home.
- Provides method to support adjacent insulation, especially if it is blown in insulation.
- Provides access to attic.
- Substantial enough not to degrade after multiple uses.