Charleston home inspector discusses general insulation requirements.

General Insulation Requirements

This is a quick synopsis of the current insulation requirements for homes in the Charleston lowcountry area. South Carolina uses the 2006 IRC code so our discussion will be limited to that application. Charleston is in the climate zone 3-a – category warm moist and “a” is the warm humid designated area.

On newer homes an energy certificate is required on the energy distribution panel. This label will tell you how much insulation is installed on the home at time of constrution.

·         Ceiling R-value 30

·         Wood framed walls R-value 13

·         Floor R-value 19

·         Mass Wall R-value 5 ( mass walls are generally concrete or concrete block type walls)

·         Crawlspace walls R-value 5/13 .  ( 5 for mass wall,13 other types)

Windows

Fenestration – This is code speak for windows – Window energy efficiency is called the U-factor. The lower the U-factor the less the heat loss so a lower number is better. To Convert the U-factor to R-factor take the number 1 and divide it by the u factor.  For example 1/u=R.  Current standard is .40 so 1/.4 = 2.5 R factor.

·         Minimum glazed window U factor is .40.

SHGC- Solar Heat Gain Coefficient – the lower the number the better - it is a measure of a windows ability to reduce heat gain.

Low – E – Low E coatings reflect direct heat radiation and thereby keep the inside surface of the glass cooler for instance. These types of coatings can be region specific which means that they way they coat the glass can vary by their geographic needs.

DP- rating- stands for design pressure and has to do with the windows ability to withstand hurricane force winds. The higher number means a stronger window.  The window size and wind speed and jurisdictional requirements vary so your code official can help here. Generally DP-35 or higher are what you will see around here.  A DP-35 window 20sf or less is good for the 130 mph wind zone for instance.  A larger window might not meet this standard. This is not really an energy efficiency rating but you will want to know what is required if you are ordering windows.

Generally replacement windows need to meet the new energy codes.

Ductwork Insulation

Supply and return ducts insulated to R-8. Ducts in floor trusses shall be insulated to R-6. All other ducts R6 except ducts inside the thermal envelope of the building.

Mechanical system piping – R-2(if it carries fluid over 105 or below 55 degrees)

Water Piping

Hot water Piping- R3 for 3/4 piping with a run greater than 10'. All other water piping shall be insulated if subject to freezing. See 2012 IRC 1103.4.2 for more on hot water pipe insulation.

About The Crawlspace Under Floor Insulation

Floor insulation shall be installed so that it maintains permanent contact with the underside of the subfloor.

Concerning the paper facing on fiberglass roll insulation. Vapor retarder shall be placed on the warm in winter side of the thermal insulation if used. Unfaced insulation is allowed to insulate the under floor areas of crawlspaces in climate zones 1-4 (Charleston area) (Recommended)Crawl space floor vapor retarders not excepted. See irc 1102.5 e., reference irc 2006 318.1 exception 2,3. References IRC 1101- 1103

In this photo the insulation is upside down. The paper facing is designed to be against the warm in winter side of the building. Also the instructions printed on each piece say the paper facing should be in substantial contact with the subfloor. It needs to be turned around and properly supported with insulation rods or other means. Although the manufacturer warns against this because the paper facing can burn in this climate zone it's more likely the paper will become damp and moldy.

   Here is an example of the information you'll find on the window label. Click image to enlarge. It includes DP ratings and energy efficiency ratings. This window has a DP 50 rating.

        At left is an example of blown in cellulose insulation. Typically made of plant fibers like ground up newspapers and magazines or denim cloth it has good insulation properties. It is somewhat heavier and denser than fiberglass and stays in place better. I've noticed also that it's easier on your lungs as it doesn't become airborne as easily as fiberglass can.   It's treated with chemicals to resist rot and fire. If you look closely you can see the ground up print material. It has a R value of about 3.8 per inch.

    At left is blown in fiberglass insulation which is very popular with many builders today. A very good insulator it is nearly fireproof, rot proof and won't absorb moisture. The R value of fiberglass can vary somewhat depending on how it is fluffed up. On older homes the fiberglass is denser and stays in place better than what you see here. This kind is easily airborne and trampled by workmen etc. thus reducing its R value in those places.  Because it is so light there will often be bare spots in the attic next to cornice vents etc. where the wind has blown it back.

Here is an example of mineral wool or rock wool insulation. It's mostly made from slag which is a type of stony waste product left over from smelting metals.  It has an insulation value of about 3.7 R per inch. It's heavier than the fluffy white fiberglass and stays in place better. It has good insulation and sound deadening properties. It's resistant to mold and is fire resistant. It can be blown in like this or in rolled batts with paper facing just like fiberglass insulation. It is also frequently used around ductwork.

Here is some asbestos pipe insulation found in the crawl space of a home which was built in 1950. Asbestos is a health hazard if it becomes friable. It appears to be a corrugated type of product here.

Here is a close up view of the corrugated  asbestos pipe insulation above.

At left is a warning label on an Air handler. It says that fiberglass can cause cancer (in California) so be careful and protect yourself especially around the fluffy stuff.