Don’t Let Your Roof Take the Heat

Tips to keep your attic cool

By Marc Richmond*

Picture this: It’s a hot and humid summer day. You head for the indoors and some relief from your trusty air conditioning (A/C) system. Three hours later, you’re slightly cooler, but you’re wondering why your A/C unit hasn’t shut off yet. Here’s why: all day long, solar radiation has been heating up your home through the windows, walls, doors and especially the roof. Your attic temperature can easily reach over 140 degrees. That heat up there is working its way through your meager attic insulation into your home and through the A/C ductwork, located in your attic, into your cooling system. Your A/C system has to fight that added heat to change all that hot air in your home into cool air. You can install solar screens for the windows, porches around the house for shade, and plant trees around the home, but what do you do about the roof which accounts for a third of all the heat build-up of your house?

Here are a few options:

Ventilate your attic with ridge and soffit vents. Vents are louvers, grills, or screen materials which allow passage or air through them. They are typically installed along the top peak (ridge) of your roof, at the top of the side wall (gable), and on the underside of your roof overhang (soffit). Ventilation moves air through your attic by force of wind or by heat rising through natural convection. This leaves cooler air sitting on top of the insulation on the attic floor. Ventilation also has the ability to remove humidity which has built up in your attic and which reduces the effectiveness of your insulation. It is often best to hire a contractor to install these.

Insulate your attic to R-30. R-30 is roughly a 10 inch thick layer of insulation material above your ceiling. This is a job for any handy homeowner or it could be handed over to a contractor. When installing the insulation, be careful not to block your vents.

Install a radiant barrier between your roof and your attic insulation. A radiant barrier is an aluminum foil material which prevents 95 percent of the heat that radiates from your roof from reaching the insulation on your attic floor. It comes in a roll and is stapled to the underside of your roof rafters, or as a metallic paint. Radiant barriers are sold in most building material supply centers and can be easily installed by a homeowner. This system can save you up to eight percent on your summer cooling bills.

When it comes time to replace the roof, use roofing material which resists or reflects heat – typically lighter colors are best, though there are some new materials which are effective at reflecting infrared radiation (heat) with a more ‘traditional’ color.

This article first appeared in the Austin American Statesman and was republished by us in 1997. *We have since edited the article.  At the time of publication, Mr Richmond was with the City of Austin’s Green Building Program; he now is president of Practica Consulting.

ASTM Standard Guide for Earthen Wall Systems

A note from our friend Bruce King:

Friends and colleagues —

I’m very happy to tell you that ASTM International has approved publication of revisions to ASTM E2392, Standard Guide for Design of Earthen Wall Building Systems.

This has been a four year project for me and for the Ecological Building Network, and you helped make it happen! This building standard now provides:
– prescriptive guidance for affordable seismic safety,
– engineering guidance where it is practically available, and
– discourages the use of cement, especially applied as render over earthen walls.

Various industries tried to stop this project, and it has been a sometimes weird experience, but we are now done. It has taken four years but was worth it, for we now have a document that we can work with anywhere in the world.

If you already have a draft from any time in the past two years, then you have something pretty close to the final language. If you want the formal document, you must order it from ASTM International, where it will be ready with all final edits by late January. Upon request, ASTM will also translate it for any country holding a memorandum of understanding with ASTM (which is most countries). http://www.astm.org/index.shtml

Thanks, and warm greetings from cool California,

Bruce King
bruce-king.com
ecobuildnetwork.org

New Topic: Shipping Container Housing

One important guideline for sustainable building is to use materials which are locally abundant. Another guideline is that waste from one system can often be utilized as feedstock for another.

Shipping containers are abundant in the US due to current trade imbalances and are therefore inexpensive pre-built modules which some enterprising people have begun using to create residences, dorms, and commercial space.

Reza Pouraghabagher has written our newest topic area on Shipping Container Housing and will be adding more in the coming months. Follow the Resource links to see some completed projects.

Atlanta area rainharvesting microbrewer can’t use rain

In an unfortunately too common incident of bureaucratic lack of common sense, an Atlanta area microbrewer 5 Seasons had to switch back to city water after officials couldn’t find any regulations on rainwater use in their books and concluded it must therefore be illegal.

According to our source the brewery “could have dug a well on the site of the former stockyard without even having the water tested” but their rainwater, which has been tested and passed with flying colors can’t be used until they receive official blessings to do so.

Support these guys if you’re able. They’re trying to do the right thing.

Last we checked, they’re on Marietta St. 

Dick Peterson joins for Rainwater Q&A

We’re happy to report that Dick Peterson, a 15+ year veteran of Austin Green Building who spent a fair bit of that time advocating, educating, and advancing rainwater harvesting in Central Texas has agreed to join us in the Harvested Rainwater section.

Dick will be keeping that section up to date and is available for Q&A (scroll to the comments section at the bottom of the page… you must be registered and logged in to post).

You can also subscribe to the Q&A RSS feed at the top right corner of the Harvested Rainwater page.

Bale Raising Sept 12

Sustainable Sources founder Bill Christensen will be leading a straw bale wall raising in conjuction with DesignBuildLive.org on September 12th outside of Wimberley, TX (about 50 min SW of Austin). Hope to see you there!

(Originally scheduled for Aug 22)

Full and registration at http://designbuildlive.org/

Neighbors and Fruit Trees

Not exactly green building, but sustainable none the less…

As long time proponents of edible agriculture and local foods, we were delighted to find the article Neighbors and Fruit Trees by Jim Hightower. The the websites referenced, www.fallenfruit.org, www.forageoakland.blogspot.com, www.neighborhoodfruit.com, and www.veggietrader.com all look useful, though the latter two are probably the ones I’m most likely to use as they’re both free and not limited to a specific geographical area. Happy eating!