Blower Door - Slight Disappointment

Ok, we had what was supposed to be the second and LAST blower door test, but I am not happy with the result and I may have Dean Benton of Benton Green Energy come again after I have fixed some problems. 

Blower door reading on August 6, 2014

You may recall that a blower door test helps determine how much air leakage you have through the building envelope. The test involves putting a fan in an outside door frame and depressurizing the home to accentuate the air leaks. The house is depressurized to a level of 50 pascals which is about equivalent to the force of a 20 mph wind on the home. There are 2 main values that you get from the test - one is directly from the manometer as shown above and one is calculated based on the volume of the house. This article, Blower Door Basics by Martin Holladay on Green Building Advisor (GBA) explains it much better than I ever could.

Blower Door Set-up while we were at the rough-in stage. 

The number shown on the manometer above is called cfm50 or the amount of air that moves through the home at 50 pascals of pressure. The other number is ach50 or air changes per hour at 50 pascals.

Our previous reading was 98 cfm 50. The above reading is 235, but I think it leveled out at 220. In any case, the number has more than doubled - 2.4 times greater than the last blower door.

What happened??

Well, I have some ideas.

What do you think about this dryer vent? Do you think that there is some leakage around this pipe?

Dryer vent through the wall, not sealed around the vent pipe. This was installed AFTER the first blower door test.

What about the vent cover for the kitchen fan? Do you think that those little plastic louvers seal out air?

This flimsy plastic piece covers one of the fan vents. A similar cover was on the dryer vent. 

Now the photo below may show a less important air leak. This is the inside view of the Lunos e2 - a heat recovery ventilator (HRV) that exchanges outside air for inside air. It does go through the wall in large tube. We did seal the tube to the sheathing inside and out before the walls were closed in. Still it is designed to move air through the home. You may wonder why we go through all the trouble to seal up every possible hole in the building envelope and then deliberately install a fan to exchange air. Well, when you have a very well air sealed home, you need to move more fresh air through for the inhabitants, but it needs to be filtered, conditioned air, not random leaks. That's what the HRV provides.

Lunos e2 Heat Recovery Ventilator (HRV)

The reason I did not calculate the ach50 is because I am confused about the volume of the house. The house is a Cape Cod design with kneewalls and sloped ceiling upstairs so I don't really know what counts as the house or not.

For example, the space above the bathroom and the bedrooms is not really sealed off from the rest of the house. It is within the thermal envelope of the building. Do I count that? I think so, but I am not sure. I am going to post a questions on Green Building Advisor to get their advice.

Area above the bathroom. You can see the Intello Plus smart vapor retarder from 475 High Performance Building Supply. The ceiling joists are insulated with dense pack cellulose. There will be a small door that fits in the opening. It does not set tightly to the frame, however. Is this within the thermal envelope?

So, the big change from the rough-in stage to almost completion (I know, almost completed at 18 mos later - crazy ) is the vents. We taped cardboard over the area where the vents were during the first test, but I don't know if you tape over vent covers when you go for the final test. That's another question for the knowledgable people at GBA.

I'll let you know more later. Thank you for visiting here. 

Roof Assembly Details - Challenges in Designing an Energy Efficient Home

I have been looking on the internet for days trying to find good photos that explain in more detail how I want to do the foam insulation on the roof. I have found a few photos that are similar to what I want to do, but not exactly. I've included a list of related references and links at the end of this blog post which might be useful if I don't explain things adequately. I have also noted the reference in the photo caption if I have posted a photo from the internet and listed it in the reference section as well.

So now for the actual roof assembly discussion.

I'd like to use a type of foam insulation called polyisocyanurate for a number of reasons. Polyiso (as it is usually called) has the highest R value/inch of the commonly used foams (EPS, XPS). It is more fire resistant than the other 2 and more environmentally benign. That is, the blowing agents used to make polyiso contribute are thought to contribute less to global warming than the blowing agents for EPS or XPS. Polyiso has some disadvantages though. It is less dense than the other 2 foam boards and cannot take much weight on top. It shrinks somewhat. See 2 articles below to Dr. Joe's barn. Dr. Lsturibek wrote about it in his article in Fine Homebuilding. And finally polyiso is still a fossil fuel product which we are trying to avoid for the most part in John's building assembly.

The plan is to place about 3.5 inches of polyisocyanurate insulation on top of the roof sheathing to provide about R-21 insulation in addition to the dense pack cellulose insulation between the rafters which provides R-33 giving a total insulation of R-54. On top of the insulation will go another layer of plywood sheathing to provide a stable base for the metal roof.

One of the challenges of installing foam insulation on the roof is that you are working at height. Another is trying to install the insulation without causing "thermal bridges" where heat is transferred easily. And finally you have to figure out how to attach the metal roof securely through 3.5 inches of foam and 2 layers of plywood sheathing which usually entails using some long ass screws.

One of the best articles I found that shows one way to install polyiso on the roof is on a house in California called the "CLAM" Blue House, the first passive house in California. First they airsealed the roof sheathing. Second they installed 2 x 4 sleepers (installed on the narrow edge of the 2 x 4) to the roof sheathing nailed from the UNDERSIDE of the roof sheathing between the rafters to prevent thermal bridging. The function of the sleepers is to provide an attachment for the plywood layer onto which the metal roof is attached. There is still some minimal thermal bridging by using the 2 x 4 sleepers but not much. Remember the R-value of solid wood is about 1/inch. It has little resistance to heat flow.

See the air sealed roof sheathing. The gentleman is spraying the sheathing with a boric acid solution to inhibit mold and prevent insect infestations. This photo is from the CLAM Blue House blog.

Photo of the installation of the 2 x 4 sleepers on the CLAM Blue House roof.  Remember these sleepers were installed from the underside between the rafters to decrease the thermal bridging through the rafters.

Photo of the installation of 3.5" of polyiso between the sleepers on the CLAM Blue House

This photo shows the sheathing over the polyiso and sleepers on the CLAM Blue House

You can see in the photos of the CLAM Blue House that they made the roof overhangs by extending the sleepers over the edge of the roof. This prevents the thermal bridging problem of using the rafters themselves for overhangs. 

Overhangs established by using the sleepers on the roof sheathing on the CLAM Blue House

Advantage of using this method of insulating the roof - relatively easy design with polyiso. Disadvantage is primarily thermal bridging and loss of insulation with the 2 x 4 sleepers.

Sometimes you have to make a "ladder extension" to make gable end overhangs. Martin Holladay wrote about it in a Green Building Advisor. These ladder extensions are built on the ground and installed on the roof sheathing. I hope to avoid ladder extensions because I think they would be heavy and awkward to get up on the roof.

Martin Holliday's drawing on Green Building Advisor drawing of a "Ladder extension" to make overhangs on the roof. 

After the 2 x 4 sleepers are installed then you add the polyiso between the sleepers. In the CLAM Blue House they used one layer of 3.5" polyiso, but I would prefer to use 2 layers because polyiso can shrink. Seams between the polyiso would be foamed and taped to provide a continuous air-sealed layer. Then sheathing on top, then roofing felt followed by the metal roof. 

Another good article is "Retrofitting an Insulated Cold Roof" from the November 2008 Journal of  Light Construction written by Dan Perkins, a builder in Michigan. He used a similar design except that he used a different foam, XPS, as a solid layer on the roof abutted against one or two layers of 2 x 4 nailer(s) on the edge of the roof. 

Layer of XPS installed on roof sheathing covered by a synthetic roof underlayment in Nov. 2008 JLC article "Retrofitting an Insulated Cold Roof" by Dan Perkins. Please note the double 2 x 4 nailer on the edge of the roof. I cannot tell if the author taped the sheets of XPS together or not.  

XPS has higher compressive strength than does polyiso, so if you are going to install 2 x 4s directly over it, it will compress less. 

Installing purlins on the first layer of XPS in the JLC article "Retrofitting an Insulated Cold Roof"

The 2 x 4 sleepers which the author calls purlins were then attached on top of the first layer of XPS perpendicular to the slope of the roof. The areas between the purlins are filled in the another layer of 1.5" XPS.  The author uses the 2 x 4 purlins to so he can attach a 2 x4 perpendicular to them to provide the venting for the roof. 

This form of roof provides a more continuous layer of insulation and avoids the thermal bridging with the 2 x 4 sleepers shown on the CLAM Blue House. Also it looks like it is a little easier to install. I don't know if you can use polyiso under the 2 x4s or if you have to use more dense foam (which we are trying to avoid because of increased global warming potential in the blowing agents of these foams.)

I also like the way he retrofits this roof as a vented roof with a perforated metal edging. He uses this method because one of the major roofing concerns in Michigan is ice dams which is not an issue in South Carolina. Download the article, it is a great article with a elegant design. 

Here is a drawing from Green Building Advisor which shows the nailers on the edge before the foam is applied.

From Green Building Advisor article on "How to Build an Unvented Cathedral Ceiling"

Another way to insulate a roof with foam is to use a product called nailbase which is similar to SIPs (Structural Insulated Panels) only with the OSB on only one side. I think you would have to use a crane to get the nailbase on the roof though. I'm not really interested in renting a crane.

How will I decide the exact insulation strategy on the roof? I've got to over the details with Randy and Carlton and John and the people at Shelter Kit. These guys know the practical aspects, not just from reading about it which is all I know. I'll keep you informed.

References:

Global Warming Potential of Foam Insulation http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-global-warming-impact-insulation

Don't Forget the Science in Building Science http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/28440/Don-t-Forget-the-Science-in-Building-Science

Foam Shrinks, and Other Lessons by Joseph Lstiburek in Feb/March 2012 Fine Homebuilding

http://www.buildingscience.com/documents/published-articles/pa-foam-shrinks/view

Foam Shrinks, and Other Lessons: Correction by Joseph Lstiburek in Building Science 2012

http://www.buildingscience.com/documents/published-articles/pa-foam-shrinks-correction.pdf

CLAM Blue House Blog http://clam-bluehouseblog.blogspot.com/search?updated-max=2010-06-17T19:04:00-07:00&max-results=7

Ideal Roof Overhang Length? Question on the Green Building Advisor QA section

Retrofitting an Insulated Cold Roof by Dan Perkins in the November 2008 Journal of Light Construction

Retrofitting an Insulated Cold Roof PDF version found on Dan Perkins Construction website

How to Build an Insulated Cathedral Ceiling by Martin Holladay on Green Building Advisor Nov. 18, 2011

Challenges in Designing an Energy Efficient Home - on vacation at Big Sky Montana

My family and I are on vacation in Montana. Most of the family is skiing, but my knees are being troublesome so I have only skied a minimal amount for 2 days.

Randy, my trusty contractor and good family friend, says  "Next year I’ll be hosting Randy’s Ski Training camp. We can do it in John’s shop. I’ll crank up the music and we’ll all do Hindu squats, power skips, jump rope, planks, roll outs, and turbo lunges just to name a few! Skiing is serious fun and it requires serious prep." 

One advantage of being a little gimpy, though, is that we actually have made some strides in designing John's home. You may recall that we are buying a kit from Shelter Kit which is basically the shell of the home. My motivation for doing that is twofold, I want to actually use a hammer and have sweat equity in the home and the second reason is that I feel like we can control the quality better if I am involved daily.

I've been a paying member of Green Building Advisor for 3.5 years. I have subscribed to both the Journal of Light Construction and Fine Homebuilding for several years. In that time I have worked hard to understand principles of building science and develop ideas on how I would want to build an energy efficient home. I've learned the importance of air sealing, vapor control, methods of insulating a home, ideas about heating and cooling a home. As a result of this study, I think I need to be onsite during the building to make sure the home is done the way I want it to be. That's a little more detailed explanation of why I want to use a kit to build the home.

Anyway, we've got most of the layout done. My brother John has an old student version of AutoCAD which we used to draw up the plans. 

This is the first floor. We are trying to group the plumbing in one corner to minimize penetrations in the roof with plumbing stacks and to simplify the plumbing. The front porch is enclosed and will be the "Cat Porch". The kitchen is to your right as you enter from the Cat Porch. On the other side of the wall from the kitchen is the downstairs bathroom. On the other side of the wall from bathroom is the laundry/utility room. 

Upstairs with full bathroom and 2 bedrooms. The house is not really a 2 story house . It is more like a  1 1/2 story Cape Cod with a 10' shed dormer to fit the bathroom better. What is drawn as the sides of the bedrooms along the long axis of the room is the 5' line. These areas may be open or they may be enclosed for storage. John could line the rooms with drawers and cabinets for a really clean look. 

I've asked Randy and the kind people at Shelter Kit to look at the plans to see if they can see ways to simplify the plumbing and for advice on window sizes and placement. Or if they see glaring problems that we have overlooked. It's not like we have the code memorized.

Carlton, our carpenter, is recovering from his horrible accident last fall where John's old pool house came down on him and he broke his right lower leg in several places (and ribs and a vertebra or two). He has pain and limps a little bit, but he is getting back slowly. He has been helping out with the plans. He researched to find out if we could use John's septic tank or did we have to install a sewer line. Thanks to Carlton's homework, we get to use the septic tank saving probably $10,000!! Whew. That is a relief. 

Another great thing about Carlton is that he knows people where you get building permits. So we have an inside connection.

So even on vacation in the beautiful state of Montana we are getting stuff done on the house.

Lessons from the Shop

I am very glad that we decided to build a shop before we build a house. You learn so much from the building process (even if I wasn’t the one swinging the hammer or nail gun). I think it is especially important if you are trying to build a different kind of house such as a super-insulated one. Here are a few things that I have learned.

Lesson 1 – Get everyone on board. Randy is a good friend as well as contractor. He hasn’t really done stuff like this before, but he is excited about learning and is receptive to these ideas. (He’s now reads Green Building Advisor). Carlton the master carpenter is invested in doing it right. So the 2 main guys are all in.

What I have to do though is show them the significance of every air gap. I plan to do blower door tests on 3 houses – first the Lenore rental house which is a work in progress, my house (which should be done, but I really haven’t finished the attic insulation) and John’s house after we close it in.

My plan is to have them at the house when we do the tests. That makes it tangible. 

The head of the insulation company apparently gets it as well according to Randy. In a previous post I talked about avoiding him because I didn’t want to argue about fiberglass. But he does teach his guys to air seal and understands its importance. Also Randy says he is a nice guy and easy to talk to.

I also plan to invite the guys to dinner and go over the principles that I think are important BEFORE we even start. I’ll pay them for their time. I need the drywall guys there as well because I don’t think they’ve ever attempted an airtight drywall approach before (ADA).

Lesson 2 – Communication is key. It’s really a variation on lesson 1. Sometimes you think and think about a problem, solve it in your mind and assume everyone knows what you were thinking. Example, John planned very precisely where he was going to put his equipment. He drew an AutoCAD plan of his equipment for Don and Buck, the electrical guys. He assumed they would put the outlets about every 4 feet where the equipment was going. They lined up the outlets EXACTLY where he mapped it out on the drawing. See the photo. They put in enough outlets so it won’t be a problem, but it’s not what John envisioned.

Back corner with carriage doors to the side and the fold out stairs  for storage above

Lesson 3 – Ignore John when necessary. My brother was adamant about not giving up square footage on the floor of the shop for either a stairway to the storage area or a small bathroom. Flat out refused. I knew he was wrong, but I could not get him to compromise at all. Everyone who worked on the building was wondering – where is the bathroom? Why didn’t they put a bathroom in it?

John is so happy about all the space.

I should have ignored him on the bathroom issue and at least put in the pipes for a “future” bathroom when they poured the concrete. I can’t believe I didn’t insist on that.

I think John learned something from that as well.

I told him for house, he can do whatever he wants except in matters of energy efficiency. That’s not exactly true but he doesn’t know that yet.

Lesson 4 – You have to be there to oversee the details. The installation of the insulation is the best example. If you are there you can insist on having it done the way you want.

You have to be there to catch little details that matter. 

Here are more photos of the shop. Just waiting on Duke Power to install the power line and for the metal roofing for the awning over the main doors.

Main entrance to the shop. Waiting on the metal for the awning

Beautiful insulated carriage doors built by Carlton and Chris

Stairway to Storage

Front wall of shop

Side wall of shop