More Insulation and Less Cathedral Ceilings is Better

New provisions in the IRC and IECC are making houses greener

Posted on Jul 23 by Lynn Underwood, GBA Advisor

Installing spray foam insulation

9 Steps to A Greener Code

Recent spikes in energy costs have increased the attention on regulatory measures that limit energy waste. Those same energy price increases have also gained the attention of President Obama, who made energy efficiency central to his stimulus package, specifying the need to improve energy efficiency in 2 million homes.

Last week we looked at air sealing, this week we look at insulating. In cold zones the level of insulation has increased, and so has the size of allowable cathedral ceilings.

STEP 2: MORE INSULATION, LESS CATHEDRAL CEILING (TABLE N1102.1 IRC AND IECC)

The code: In numerous areas of Chapter 11, insulation requirements have been increased or trade-offs that allowed for insulation reductions have been removed. This effectively improves the thermal envelope to retard heat flow. For example, floor insulation increased in two climate zones; basement insulation increased in several climate zones.

What it means to you:
In colder zones (5-8) there is a small but effective increase in insulation in walls, floors, and basements.

In addition to these modest increases, there was one significant change. Cathedral ceilings tend to have limited insulation and can account for large energy losses. The IRC has now limited the size in which you can build cathedral ceilings to either 20% of the entire ceiling area or 500 sq. ft., whichever is less. Basement insulation was also added to portions of Climate Zone 3 where, previously, you were not required to install it.

While some of these code changes occur only in the IECC and not in the IRC, it is important to note that either energy code can be used for those building single-family homes. Generally, the added costs of increased insulation material will be minor and the labor costs should not change, compared to the energy savings realized.

The 2009 building codes reflect practices that not only increase energy efficiency—air-sealing measures and increased insulation, for example—but also address sustainable building practices, such as moisture control.

Other segments of this series:

Part 1: Air Sealing
Part 2: Insulation
Part 3: Lighting
Part 4: Programmable Thermostats
Part 5: Insulating Mass Walls
Part 6: Efficient Windows
Part 7: Insulating Mechanical Pipes
Part 8: Exceeding the Energy Code
Part 9: Vapor Retarders

Tags: IECC, insulation, IRC

Jul 23, 2009
7:02 PM EDT

Above Code Programs - great option
by Mike Guertin, GBA Advisor

One way I've been able to 'avoid' some of the prescriptive limitations (like the cathedral ceiling limitation Lynn points out) of the building code is by using N1101.8 Above Code Programs. This permits the local official to deem an energy efficiency program to exceed the code requirements. This provision is unchanged from the 2006 IRC so I've been using it for a few years. I get my projects certified under the Energy Star Home program and submit the approval certificate to the building department.

Oct 3, 2009
9:44 AM EDT

BS
by greg

Wow! You are proud of the way you are getting around the fact the foam IS BUSTED. No more using R-19 on a 4/12 roof pitch and conning people into believing it is better than r-60 loose fill on the ceiling for more cost! So you just get some ignorant energy auditor that you have sold on foam and DEFY the 09 IRC's logic, and fck the customer over.

Nov 24, 2009
8:28 PM EST

Ass-umptions?
by Michael Chandler, GBA Advisor

I hardly need to come to the defense of Mike Guertin, his integrity and commitment to the improvement of the way people build homes is well documented. But I have to take issue with folks who make inflammatory comments such as this one by "greg" who doesn't give his full name, uses abbreviations like "BS" and "fck", and attacks Mikes comments by assuming that he is talking about spray foam when he is actually talking about finding a way to build an energy star home with a cathedral ceiling that is more than 20% of the ceiling area.

My partner, Beth Williams, recently designed a house that is 100% cathedral ceiling (R-38), uses 2-3 kilowatt-hours per day (equal to a 100 watt light bulb) and has already paid back all the electricity used on site for it's construction.
http://www.frogpondfarm.org/houseConstruction.html

Cathedral ceilings don't automatically indicate use of foam, and my energy auditor certainly wouldn't credit 6" R-20 foam as better than R-60 "loose fill" (code for cellulose?) People like this who jump to assumptions and vitriolic language while posting anonymously do nothing to forward the cause of reasoned and intelligent discussion of the complex issues presented by the code and green building practices.

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About the Author

Lynn Underwood is a building official with the city of Norfolk, Virginia. He has worked in the building safety profession for 25 years. Lynn has written five books on construction, most recently, Your Green Home. Read more...