3.05.2009

Your house sucks (outside air at least)

Welcome to the first edition of my newsletter about the current state of green building. I will try to spare you from too much cheerleading about how great the green building movement is. Nor will I overly promote my consulting company Baosol and how useful our services are. I will send you these newsletters in the spirit of entertainment, accuracy, and importance. Just a word of warning though, I find science to be very entertaining as I’ll start with a building science story.

Ok, here’s the awful truth, your house really does suck. It sucks so bad that an entire small industry has developed based on this fact. An Energy Rater, as many of you know, has the enviable task of finding the little holes in your house that let all that lovely expensive conditioned air escape, and all that fresh damp, cold and hot air come in. Why does the Energy Rater have such an enviable job? Because you pay a lot of money for heating and cooling, you add a lot of green house gases to our eggshell thin atmosphere (sorry global warming deniers), and you are not comfortable. Rarely do such vastly important issues come together. An Energy Rater can help resolve those issues.

Here is the entertaining part for me; building science. My personal story about why your home sucks begins in the year 1994. New to Colorado, I go looking for a job. On the job board is “sheet metal installer $6.50/hr to start”. Ok, I can live on that. So they hire me and I enter the vast world of HVAC. Really, all I did was install all that shiny tin you have in your basement. Our weapon of choice was “duct” tape. Now “duct” tape’s name is a brilliant marketing strategy because it should never be used on duct work, but back then always was. This is not the science part yet, by the way. It did not take a scientist to figure out that cheese cloth and glue were not going to last long in a hot/cold dry space, under pressure, for very long. All those ducts I slipped together, and in the proud company’s tradition of neatly wrapping the seams with “duct” tape, ending at the top where you can’t see it, have now failed. This means lots of air spewing into floor cavities, attics, and crawlspaces. By the way, we never even used “duct” tape for the returning air, we just used the drywall and floor joist to do the work. “Big deal”, says the HVAC industry, “the air is still in the building.”

If you have just read the paragraph above you should be sensing a bit of discomfort in my tone. If you haven’t, go back and read it before we proceed with our story. Back then the HVAC industry made stuff up. They said, “Don’t worry, all that conditioned air you paid for is still in the building, but since a couple of rooms may be a little uncomfortable we’ll just put in larger equipment to make up for it.” So the energy issue gets worse. I don’t know if they didn’t know or didn’t care about the science of how air moves. What was not talked about was pressure. Commercial HVAC designers, to be fair, understand pressure like their life depends on it, well maybe just their jobs. What they know is that if you put air in one place it pushes air somewhere else, but even more important is if you take air from one place it will be replaced with air from somewhere else. Trouble starts when that somewhere else is not where you intended it to be. So your house has all these negative and positive areas of air pressure. Your inevitably leaky supply and return duct work wants to push and grab air from where ever it can. An interesting fact is that a big place that air gets into your home is the connection between the foundation and the wall on top of it. This is unfortunately also where your negative pressured, unsealed return air is. So every time you want to be a little warmer, a little cooler, or just move some air around you are sucking in outside air like a vacuum cleaner. Got holes in the house somewhere else? In a pressurized room this is a great place for all that lovely conditioned air to escape. A little depressing really.

Solution: seal duct work using mastic, and a “hard” ducted return air, and seal your house. The nice folks who do those whole house blower door tests also can perform a duct leak test. Though fixing what they find is often not quite so easy. Now, for the folks who like the fresh air, myself included, would depend on this leaky air, and then complain about the bill. The new building mantra goes as follows: “Build tight, ventilate right”. No top 40 song potential but you get the idea. Control the air that comes into your home with a heat recovery ventilator or HRV. Hey, you can even filter that air too.

If you got this far in the first of Baosol’s Sustainable Line newsletter you may be interested in what else makes your house suck. Your hot water heater’s flue, your furnace flue, your bath fan and your kitchen fan. Get a sealed combustion furnace and hot water heater, use that HRV to make up for that lost ventilation air. The leeward side of your home is letting all your heat out while the windward side is feeding cold air. And let’s not forget all that moisture that comes into your home too, it may not make it to your living space but sit in the wall instead.

If you are building new, consider not using a furnace. Hydraulic heating in your walls, floor and ceiling are great, and if you build tight with some good r-value you may need little or no air conditioning. Want to talk about payback? You’re more comfortable and the money you spend up front is recovered in your lowered bills. What’s next? A plug and play solar thermal heating system, nice work.

Now your house doesn’t suck.

Just for fun, check out the website seeimgreen.com and add your pin and principles to the world map.

Be well and stay tuned for the next edition of Baosol’s The Sustainable Line, as I will “Report from the front lines of near zero”.

Andrew Michler

1 comment:

  1. I urge you to look at what Miranda Homes is doing. It's a holistic look at a home rather than a sum of parts. Our blog runs a nice parallel with yours.

    www.mirandahomes.blogspot.com or www.mirandahomes.com

    ReplyDelete


"If you want to make it in this world you gotta' adapt" -Muddy Mudskipper.