Compressing Insulation In Attic

We can compress insulation and increase the performance of it right up to the point where the main mode of energy transfer is through the material of the insulation itself.

Compressing insulation in attic.

For the center areas hold the hose level and blow in insulation evenly until you ve reached your level lines photo 6. Lay a two by four on top temporarily compressing the insulation to a manageable. Subtract the cavity depth from the thickness of the batt in inches. Let s look at an r 19 batt in a 2x6 cavity step 1.

The chart below indicates the compressed r value of standard building insulation products. Achieving greater r values in attics the higher the r value the better the thermal performance of the insulation. To cut blanket style insulation place the product over a piece of plywood with its paper or foil side down. There was no plywood up there plus it looks like the insulation is not uniformly compressed.

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. R value simply means resistance to heat flow. For wool types of insulation fiberglass mineral wool steel real wool etc while it varies based on material this is typically much denser than we are able to get it via compression on the job site. When installed in framing cavities with a depth that is less than the labeled thickness of the insulation.

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. For every x the insulation material is compressed the r value decreases by approximately one half of that percentage or x compressed. Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target r value and. Then pivot in place and do the same thing to the other side.

Yes the compressed r value can be estimated using the following method. When compressed to less than its labeled thickness glass fi ber insulation will experience a reduction. These thermal defects not only undermine the r value of your insulation but they also make rooms uncomfortable and increase your utility bill. 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.

If you know you aren t going to convert the attic in the future that leads you one direction compressing the insulation is fine maybe you don t care so much about head height and can add some more thickness to improve the insulation etc and if you know that an attic conversion is viable and that you are likely to want to pursue that in the future you can plan accordingly.