Insulation Manufacturers and Contractors Make False Energy Saving Claims

Attic Myths & Misconceptions

This article attempts to address some of the myths and misconceptions surrounding attic insulation, attic strategies and insulation products. We routinely meet with potential customers on estimates who are genuinely confused and not sure who to believe in the marketplace. This article attempts to sort through the noise.

Our goal is to provide our customers with credible resources so they can make more informed decisions. When possible we cite independent third party resources to establish our opinions. We’ll also highlight your utility company’s newsletters and rebate programs. It should be noted that provide rebates for proven energy efficiency strategies.

1.One Solution?

Many companies want you to believe if you invest in their one product or service, be it a attic insulation, radiant barrier, foam insulation, attic ventilation, powered attic fan, etc. that you will dramatically reduce your utility bills. The truth is no one product makes a home energy efficient. If you want to save energy you need a comprehensive solution that is tailored to your unique problems. This is why we are such ardent supporters of your utility company’s $99 energy audit, which will identity the most cost effective and proven combination of solutions to reduce your utility bills.

2. Attic Heat Gain

We routinely perform Manual J thermal analysis when we size air conditioning equipment. A well-insulated and air sealed attic in Phoenix will only comprise 10% — 15% of the sensible cooling load. In other words, when you get the basics right, your attic insulation and air barrier, you then need to focus on other energy conservation strategies like duct sealing and shade screens.

3. Radiant Barriers

Radiant barriers are highly reflective materials designed to block radiant heat transfer. Research conducted at Oak Ridge National Laboratory has shown that the effectiveness of radiant barriers is minimal, if you have proper insulation

Many radiant barrier manufacturers aren’t telling the truth. The following ad is completely fallacious: “Regardless of how much insulation you have in your attic, adding radiant barrier will save on your heating and cooling expense, and keep you more comfortable. Energy savings vary from 17% to 25% …” When radiant barriers are sold for more than $1 or $2 a square foot to consumers they fall into the category of a scam.

Radiant barriers can’t compete with proven energy conservation strategies like duct sealing, shade screens and adding more insulation. Advantage Home Performance will not sell or install radiant barriers in homes because we believe they are a poor value for customers.

Dirty radiant barrier over a 2” of rock wool with an R-value 5 — 7

Furthermore, dust storms will drive dust into attics through attic vents and this dust will accumulate on radiant barriers installed on an attic floors and thus reduce their effectiveness. Radiant barriers reflect radiant energy and dust undermines their reflectivity. Examine the dust on the radiant barrier in the photograph above. If a radiant barrier is multi-layered it will compensate for dust, but if this multi-layered product cost more than a blown in insulation it is a bad value. Conventional insulation still works fine when it gets dusty.

Dust covered radiant barrier – eve vents in background

Ask yourself, why are the Arizona’s four largest utility companies giving rebates for air barrier work, duct sealing, insulation, shade screens and mechanical equipment upgrades, but not radiant barriers? They are not giving rebates for radiant barriers for the same reasons we refuse to install them, which is because they are not a good investment.

Insulation Manufacturers and Contractors Make False Energy Saving Claims

4. Passive Attic Ventilation

Passive attic vents are the vents installed in attic during the construction to let moisture escape from an attic in the event moisture gets into the attic. Many homeowners falsely assume that since their attics are extremely hot in the summer the best way to reduce their cooling load is to get the heat out of the attic. The problem is that most naturally ventilated attics don’t have enough air exchange to make a difference.

Research done by Professor Bill Rose, Research Architect, Building Research Council-School of Architecture University of Illinois, found that “in roof cavity assemblies which are poorly insulated (less than R-10), ventilation can reduce cooling loads by 25 percent. However when these assemblies have thermal resistance greater than R-25 ventilation has a negligible effect.” If an attic is under-insulated the solution is insulation, not attic ventilation.

Older home with asphalt shingle and turbine vent

Heat gain through a well-insulated ceiling represents a small amount of the total sensible gain. In The Moisture Control Handbook written by Joseph Listiburek and John Carmody it states that “where roof assemblies are tight and well insulated, ventilation of roof assemblies has a negligible impact on cooling loads.” p. 71

5. Attic Baffles

An extension of the passive attic ventilation myth is that attic baffles are essential to maintain attic ventilation. They maintain an air space between the vent at the frieze block and the roof sheathing.

Leave a Reply