Compressed Insulation Attic

Simple thermal analysis reveals that if you have 5 missing insulation in an attic bare sheetrock you ll have a slightly more than a 54 drop in r value.

Compressed insulation attic.

There was no plywood up there plus it looks like the insulation is not uniformly compressed. I have a question for you regarding what you wrote. You can compress fiberglass insulation as much as you want i am trying to make a shower niche on a 2x6 exterior wall in which fiberglass insulation already exists. Achieving greater r values in attics the higher the r value the better the thermal performance of the insulation.

To make a niche i want to compress the insulation quite a bit down to only 1 5 or 1 75 inches. These thermal defects undermine the r value of your attic insulation. The chart below indicates the compressed r value of standard building insulation products when installed in framing cavities with a depth that is less than the labeled thickness of the insulation. When compressed to less than its labeled thickness glass fi ber insulation will experience a reduction in r value.

The floor insulation can simply be left in place if you re now heating the attic. Yes the compressed r value can be estimated using the following method. Batt and roll insulation and loose fill sometimes known as blown in insulation. See install batt and roll insulation for details.

Subtract the cavity depth from the thickness of the batt in inches. There is a path down the center of the attic that has the top 6 inches of insulation above the joists that appears to have been compressed by either some one crawling across the attic or laying a piece of plywood across the joists. Loose fill blown in insulation is best for tight spaces or if your attic already has a layer of insulation. Let s look at an r 19 batt in a 2x6 cavity step 1.

When it s time to re roof adding 2 of roofing polyiso or a 2 5 polyiso nailbase panel would be sufficient to beat code minimum performance on a u factor basis due to the r11 thermal break over the rafters. R value simply means resistance to heat flow. Grab a tape measure and a flashlight to see what kind of insulation you already have in the attic and how deep it is. There are two main types of insulation.

Then use the numbers in the chart at right to estimate its r value. Find your zone on the map and then use the chart to determine the level of insulation you need to properly insulate your attic walls floors and crawlspaces. For every x the insulation material is compressed the r value decreases by approximately one half of that percentage or x compressed.