Case Study – Rain Screen

It is increasingly important to correct energy problems in older homes. In many cases, correcting insulation in the roof, upgrading mechanical systems and weather stripping in doors is simple. These are the most typical corrections to make. But in some cases there might be a glitch that makes it difficult.

Here is a case study of a home in Elgin. This is a small low end track home on several beautiful acres. There are plenty of trees on the lot, but no significant shade over the house. The couple had recently remodeled the interior of the home with expectations of selling, but then changed their mind and decided to sell their home in Austin and live in Elgin. The home also had very poor wall and roof insulation. The wall insulation was expected to only be about R-9.

The couple plans were to add square footage on the North side of the home, add an outdoor living patio on the East side and a front porch on the South side. With much of the roof structure remaining in tact and with the additional square footage, we specified open cell spray foam in the rafters of the roof system to handle the insulation problem in the attic. We also specified a metal roof to give the look they wanted with the added green advantage of lower energy usage that metal gives.

The walls were a more difficult challenge. With the newly remodeled interior, we didn’t want to remove sheet rock on the inside of the home to reinsulate the walls. On the East side and much of the South side, the patio cover was to give us the extra protection to the walls, but with the new North side addition, we had a long West wall with no protection. Extending overhangs gave us a little help, but we really needed more protection. The only way to correct the problem was to go into the walls from the outside, but to remove everything including the wall insulation was cost prohibitive.

We specified to remove the old siding down to the plywood sheathing and add a layer of rigid foam insulation to the outside, then a house wrap over that. With this ridid foam insulation, you can get anywhere from an R-2 to R-10 depending on the thickness of the material.

On top of that, we detailed a rain screen for extra protection. A rain screen has airspace between the house wrap and the siding. The purpose for the air space is to keep the house wrap dry, preventing capillary action from wicking water up into the wall that can sometimes happen when it rains. This also allows water from either rain or condensation to drip down out of the wall. The other purpose is to create an air flow not only for drying but cooling the wall. This is done simply with furring strips and a screen to keep pest out of the wall space. The space at the bottom and top of the siding allow for the air flow.

This detail gave us the added protection of air flow and “shade” on the long west wall and made up for the less than standard existing insulation. It is such an easy detail that we specified it on all 4 sides on both new and old walls.

Let us try it out on your house!

Green Living Tips!

I welcome inspirations from your home to put into future newsletters. Email them to me; Cammi Klier. Thanks!!

If you don’t have a grey water collection system in your home, but your dry grass is driving you crazy, buy a simple pond pump, some as low as $11.00 at Pondepot. Pump your bath water onto your thirsty grass after a 107 degree Austin day!

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