Why should General Contractors spot check their insulation subcontractors?

Insulation Insulation needs to be treated like an essential house system, not just a necessary evil. Tremendous gains can be made by simply achieving the R-values specified on the plans. Insulation crews need to understand that there is a large energy penalty when they leave low spots or gaps that allow air to flow freely around the insulation. It's easy for insulation crews to cut corners if their work is never checked. The builder should require a certificate of coverage from the insulation contractor and inspect each insulation job to ensure that the insulation crew took all of the following steps:

. Thorough inspections are vital for quality control. Here the builder crawls over a joist to measure the depth of blown-in insulation before signing off on the insulation.

• Use sprayed-in insulation (wet-spray cellulose or a sprayed-in foam) instead of batts in exterior walls. Cellulose and foam insulation cannot be "fluffed up" and provide true r-value per inch, unlike fiberglass batting.
• In the bathroom, insulate behind fiberglass tub enclosures when these are installed against exterior walls.
• Insulate dropped ceilings over closets or bathrooms.
• In homes with vaulted ceilings, insulate kneewalls.
• Insulate the attic access hatch if it is in conditioned space.
• Insulate the rim joists in two-story homes.
• Bring insulation into contact with the subfloor in crawlspaces.

When insulation is not thoroughly inspected by the builder, insulation contractors do not get feedback on their work and quality often suffers. Other trades--for instance, wiring, plumbing, or roof sheathing contractors--are usually held to a higher standard of accountability. Thus, the actual effective R-value of installed insulation may be well below the value specified on the plans. It's up to you to make sure that your homes are insulated correctly BEFORE you get complaints of high utility bills from customers 6 months after they move in. Or worse, you DON'T get the complaints, they just talk about it to their friends. "Yup. ABC Builders builds a good looking home, but they are sure high dollar to heat and cool." is not something you want said about YOUR business. Especially when you can control it by using insulating materials with inherent quality control features that eliminate all risk of being "cheated".

A thorough inspection involves a complete visual examination of all attic spaces, walls, and crawlspaces. Inspectors must climb into the attic and through the crawlspace. Simply lifting the access hatch and peering into the attic does not constitute an inspection. The harder it is to inspect a space, the greater the likelihood of insulation problems.

Basic Air Sealing

Air sealing efforts should focus on getting the big leaks and controlling pressure differences in the house (see "Air Sealing in Occupied Homes," HE Nov/Dec '95, p. 33). Pressure differences can occur due to duct leaks and an inadequate number of returns. Sealing the ducts and air handler, providing enough returns or pressure relief (transfer grilles) for closed-off rooms, and correctly sizing the ducts will help keep the house operating at a neutral pressure (see "Duct Improvement in the Northwest," p. 21).

A blower door test provides vital information to both the general contractor and the technicians doing the air sealing work. The test does not take long to perform, and the feedback that the test provides to workers is invaluable. Simple air sealing techniques, coupled with insulation that assists in air sealing, should easily reduce leakage in a new house to less than 3 air changes per hour at 50 Pascals (ACH50).

Effective air sealing will only occur on a widespread basis if the process is simplified. Subcontractors make money by doing the same thing day in and day out. Every time a step is added to the process there is a greater risk that something will be missed.

The construction process can be simplified by using materials with inherent quality control, such as cellulose, radiant barriers and/or sprayed-in foam insulation. The performance of fiberglass batts depends too much on the quality of the installation and even perfect installations suffer from the battings inability to retain. Batts can be installed in such a way that their rated R-value is compromised by as much as 30%-60%.

Wet-spray cellulose, spray foam, or alternate wall systems combine air sealing with insulation. These systems should be coupled with sill sealing and applying an expansive foam around windows and plumbing and electrical penetrations in top plates.

Close this window to continue