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Passive House Design: Energy-Efficient Doors

1/27/2011 1:05:41 PM

Tags: passive house design, mark miller, passive house, passive house standard, energy efficiency, energy efficient doors, doors, air infiltration, air tightness, insulation, gaskets

Mark A. Miller is a practicing architect/builder/developer living in Chicago who designs projects around the country. His studio, Mark A. Miller Architects + Builders, designs and builds high-performing, energy-efficient homes that speak to the soul. Mark recently co-founded the Passive House Alliance Chicago and is lecturing about the Passive House standard throughout the Midwest. You can learn more about his unique approach to designing thoughtful homes at his websites: Zen + Architecture and Passive House Midwest. 

I wanted to start to go through some of the techniques that help one achieve the Passive House standard. We spoke last time about the air tightness, and I wanted to continue this discussion a little further into one element in particular, a weak link in our wall system, that is our entry doors.

I recently moved our family into an older home on the northwest side of Chicago. The front door was similar to most American front doors, about 1 3/4-inches thick, little to no insulation, and minimal attempts at weather stripping. We noticed right away that a huge amount of cold winter air was coming inside our heated space, as there wasn’t much of door sweep. So, being the energy-efficiency nut I am, I went down to the local hardware store to see what I could buy, off the shelf, to improve my situation.

I found a insulating product called “Twin Draft Guard,” which is designed for folks in this unfortunate situation like myself.  It’s basically a long sock with two long compartments connected by about three inches of material.  The idea is to insert a one-inch diameter tube of foam in each compartment and slide this under your door.  Each tube of foam is to nestle up on either side of the door and seal any gaps between the door and the threshold. Well, be careful here. Out of the box this product does not work. Most doors are 1 3/4-inches thick, and the material between the two tubes of foam is 3 inches. That leaves 1 1/4-inches of space that doesn't allow the tubes to nestle up to the door and stop air from pushing in.

My letter is on its way to this product manufacturer, but I was able to fix the product. I happened to have some foam “Backer Rod” left over from my handy “City of Chicago Home Weatherization Kit” I was fortunate to get at my kid’s school’s holiday fair. I added a length of 3/4-inch diameter backer rod to each sleeve, which forced the foam tubes closer to the door, and hey hey, it now works fairly well. 

OK so what have learned here?  The state of doors in this country are quite poor in meeting the energy efficiency desires of today’s green community. Let’s take a quick look at what the German building products companies are producing to give us a little benchmark comparison of how much room there is for improvement regarding this item.

Passive House door 
Three gaskets stop air infiltration. Photo Courtesy Mark Miller. 

If you look at the photo here, you see a door from a building products expo in Germany. This was shared with us during my Passive House training. Let’s look at the upgrades this product offers:

• Insulation, what a novel idea. This door is a good five inches thick. You can see in the photo that the body of the door has a good 3 1/2 inches of solid insulation, which improves the door's R-value exponentially over our U.S. doors. Ever been in a commercial kitchen?  Imagine the doors of a walk-in cooler. These too are four inches thick and filled with insulation to keep all of that expensive freezer air in, and the hot kitchen air, out to save money. When we can improve the R-value of our doors, they will start joining the effectiveness of the R-value of our wall assemblies.

• Gaskets: You will see on the frame of this door that there is not just one compressible gasket to stop air infiltration, but three!  If the first one doesn’t stop everything, the second or third certainly will. I like to call it “Belt and Suspenders” as my mentors would always drill into me to always have a backup in case the first line of defense fails.  You will find all three gaskets on all sides of these doors: jambs, head and sill. I have contacted two friends of mine who are door fabricators and have encouraged them to be the first to offer this in the U.S. (If you have heard of anything out there I am not aware of, please email me.)

One last interesting item regarding entry doors and passive houses: most folks are familiar with a long running technique in this country where a home has an "entry vestibule" or an "air-lock".  This is the little room with coat hooks or small front porch that let’s us get out of the winter winds, so when the entry door to the living space is opened, cold air does not rush in. Great idea, but oddly enough, this is not needed in a Passive House.  Turns out the air pressures are so evenly balanced due to the home's design and ERV (energy recovery ventilator) that when a front door to the exterior is opened in the winter, cold air does not come rushing in, nor our conditioned air out. It’s counterintuitive, but the director of Passive House U.S. tells me this is the case on her own Passive House.

So, be conscious of the exterior doors in your home to limit the air-infiltration issues until the time when U.S. door manufacturers join us on the high performance, energy efficiency bandwagon.  Send letters to your favorite companies asking them for this type of product.  Your intentions and dollars may just persuade these companies to up their game. If you want to read further into this subject, check out this recent article from Green Building Advisor

Read more thoughts from Mark Miller on Passive House design! 

Editor's Note: Natural Home does not recommend, approve or endorse the products/services offered by companies guest bloggers review online. You should use your own judgment and evaluate products and services carefully before deciding to purchase.  



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