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superinsulation, how I did it.  RSS feed

 
Troy Rhodes
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I have had a couple questions to describe how I have insulated my house to "super" levels.

House 1 I built from scratch in Ontario canada.  walls were 1 foot thick, using a 2x4 on the outside wall, and a second 2x4 on the inside wall.  The space in between was filled with fiberglass, which I wouldn't do again.  I like cellulose better now.

The house had windows that added up to about 15% of the square footage.  Most were on the south (long) wall.  A few were on the east and west "ends" of the house.  There was exactly one window on the north wall.  A small one for a bedroom.

The basement was insulated on the outside with 2" blue stryrofoam, the inside was insulated with 5 1/2" of Roxul, a mineral fiber insulation that is somewhat more moisture resistant than fiberglass.  The basement floor was insulated with 4" of blue high density styrofoam.

The attic had more than a foot of cellulose blown in.  We did a near perfect job on the house wrap (tyvek/typar) and a near perfect job on the vapor barrier to reduce infiltration losses.

We had a tiny fan that pushed exhaust air out all the time, approximately 1/20 of the volume changer, per hour. 

Here are some general design principles for this kind of house.

If you go much over 15% of your main floor square footage in windows, it will overheat in the daytime if it's sunny, and it will lose heat to rapidly when the sun isn't shining, cloudy days, or night time.  Movable window insulation mitigates that somewhat.

Windows on the south can add a significant contribution to winter heating.  East and west windows are doing good to "break even", that is, to accept or generate as much heat as they lose.  North windows are net energy losers every time.

Thermal mass stabilizes the indoor temperatures, but thermal mass does not magically make heat.  In my current superinsulated shop, which has a lot more use of thermal mass, it was surprising how long it takes to heat it up, once cold.  If you have a lot of thermal mass, "turning the furnace on" has almost no effect in the short term of 20 minutes, so coming home to a cold house with a lot of thermal mass just means you're going to cold for a good long time.

In ontario, my heat loss numbers started to look really good as I got above r-40.  I went for r-50, since there wasn't much cost difference with this kind of wall system.  Since I was using an inner stud wall AND an outer stud wall, I could use studs every 24" instead of every 16", which helps on cost a little, and reduces heat losses through the framing.  Wood is, comparatively, a lousy insulator.



House #2, in Michigan.  I am retrofitting an old farm house by removing the plaster and lathe to expose the original wall framing.  I am removing the (pathetic) original insulation.  We install tyvek on the old exterior sheathing, but on the "inside" surface.  It's fiddly and time consuming to wrap it around each stud, but it helps a lot with airtightness.  Then we build an inner wall, 24" on center, add out new wiring and plumbing, put up a new 6 mil polyethylene vapor barrier and dry wall.  Once completed, we blow the wall full of cellulose insulation, a whole foot of it.  Seal the holes up well and boom, you're done.

That was a joke.  It is a hideous amount of work compared to a new scratch built house.  But we wanted this house, and I decided if it could be done with a hideously inefficient old farm house, then it could be done anywhere.

This works equally well down south to reduce cooling costs.  It does take some adjusting of expectations.  It just does not seem right that a window air conditioner can cool a whole medium sized house, but it can.


It is possible to do spreadsheets and figure out what your payback period is. In some mild climates, r-50 is too much.  but the additional cost, once you have built a double wall structure, is minimal.  The problem with calculating payback periods and Return On Investment, for me, is it's not really about the money.  It's about not using up the resources crazy fast in a couple of generations and watching 2 or 3 billion people starve as a consequence of our collective inaction.

The biggest problem with most houses in difficult climates, hot or cold, is the 2x4.  There is just no way to put enough insulation in there to get decent thermal performance.  So, we need thicker walls somehow. 2x6 with 2" foam strapped to it is not too bad for many climates.  2x6 with foam inside and out can get you a little better performance, but the labor costs now approach the additional framing costs for a double wall.

Good windows help somewhat, but you have to recognize that a terrible window is r-1, and an awesome super expensive window is r-5 maybe.  Moveable window insulation helps a lot to reduce the heat gain or loss.  There is also some evidence out there that even "high performance" windows may slowly lose their magic argon gas and end up with the same performance as a cheap double pane window. 

There are some important subtleties, like a plan to control moisture in the wall cavities to avoid a sick house with mold in the walls, or a condemned house with rotten framing.  Controlled ventillation with air to air heat exchanger helps, as does keeping the house at a slight negative pressure so that cold dry air seeps in through the walls, instead of warm moist air being slowly pushed out through the walls and dumping that moisture when it hits its dew point inside the wall.

I also like the idea of superinsulation as an aide in resale.  If I have to sell my house in 20 years, these levels of superinsulation might not give me a huge return on investment, but it may very well  make it possible to sell, where a conventional house with a $2,000 a month heat bill, might not sell at all.

It was a long and sad realization when I became aware that my conventional house was just designed poorly, and that nothing short of drastic action to attain thick walls would fix it.

Of course, part of the answer is that we should perhaps give up the idea of running around the house in the winter time with shorts, tees and flip flops.  Insulating and/or heating the human is orders of magnitude cheaper than insulating the house.

Questions are welcome,

troy
 
                        
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Location: Iowa, border of regions 5 and 6
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So, in short, you eliminated any direct thermal connection (or at least minimized them) between the inside and outside?  Do you think that having (for lack of a better phrase) inside and outside window panes would help with the insulation?  (By that I mean you have one set of windows on the inside of your 1-foot wall and another set of windows on the outside, so you'd have to open both in order to get a breeze through the house.)
 
Troy Rhodes
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Excellent question, but no.

Each layer of glass adds about r-1, mostly because of the additional air space.  This air space works better when it is filled with certain inert gasses like argon, which slows the heat transfer across the gap. 

Surprisingly, the thermal performance gets worse if the gap between the panes is much bigger than 1/4".  In a small gap, the gas acts viscous and doesn't move very much.  With a bigger gap, it can set up convection loops where the cold gas against the outside pane falls quickly (relatively), and the warmed air against the inner pane rises quickly, providing for effective heat transfer from the hot pane to the cold pane.  That's exactly what we don't  want.

So, double pane is better than single pane.  Triple better than double.  Quad better than triple.  But quad glass windows are pretty rare.  they get expensive and heavy and start to look tinted because each layer absorbs some of the light.


Finest regards,

troy
 
                                
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Hi Troy, so I think your have built a modern house that does not breath without a fan. It's super insulated, but super closed?? Have you opened up any walls to see if there's any condensation on the vapor barrier or tyvek or between the blue foam and the foundation-concrete or concrete block foundations hate trapped moisture, as they do not breath very well. I'm not trying to criticize, just trying to understand the long term benefits. It's easy to pour on r-value, but making a healthy, sustainable, long lasting house is another thing. Living and working in Toronto for 20+ years, I can't count the number of basements that where insulated in and out with major structural and health issues. I've had to rebuild foundations because of trapped moisture. Remember, what can be kept out can also be trapped in. Water will get behind the blue foam and migrate trough and maybe condense on the vapor barrier and make it into the roxel and the wood. Bam, you have moisture and mold problems+rot and foundation damage. You can't fight water, you can only work with it's nature. The best water proofing is simple grading
 
Troy Rhodes
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Yes, moisture control is critical.  But that's true in all houses. 

And it is no guarantee that a leaky house will not have water problems due to condensation in the insulation.  Plenty of leaky houses experienced structural rot because moist warm air could migrate through the wall and condense at the dew point, inside the wall. 

A leaky farm house could experience >10 air changes per hour under adverse circumstances.  These houses are almost impossible to heat to a comfortable level, despite huge energy inputs.  Adverse conditions would mean very cold and windy outside.  But on a still day, these houses could also experience stale air due to lack of natural exchange.

So, how "leaky" should I make my house to insure no moisture problems?

My approach was to use a tiny fan to introduce 0.1 Air Changes per Hour, all the time.  This takes a modest amount of electricity to operate and since it induces a slight vacuum in the house, virtually guarantees dry happy walls when used in concert with a good tyvek wrap and a good polyethylene vapor barrier inside.


Finest regards,

troy
 
                                
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Actually, moisture control is not a big issue when the house can breath. I think that is one of the biggest lies perpetrated by the modern construction industry, "moisture is bad". There's a difference between breathing and a leaky house. You did not address what happens when moisture does get behind tyvek and vapor barrier-it will get in. As someone once said "the second law(thermal dynamics) is a bitch"  The key is to not fight it but work with it, not try to stop the moisture. You can't really "control" moisture- maybe in the short term, but not in the long!
Maybe I'm missing something, but how does creating a slight vacuum in a house, virtually guarantee a dry wall. Correct me if I'm wrong has I'm always open to learning, a fan may remove moisture, but the vacuum will draw in air and moisture. No matter how moisture proof you make something, it will get in( second law again). So creating a vacuum propagates moisture through  stick frame walls, insulation and trough masonry walls. The same material that tries to keep it out will try to trap it in.

cheers
glen
 
Troy Rhodes
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Let's assume you don't have bulk liquid water getting into your wall.  And if you do, there is something drastically wrong with how the house is built.

So, if there's no liquid water getting in, then we still have to worry about water vapor.

Let's imagine it's in the middle of winter, and it's cold outside, warm inside.  The wall exhibits a temperature gradient from cold (though not as cold as outside) to warm (though not quite as warm as inside).

Even if it's "damp"  cold air outside at 100% relative humidity, as the colder, moisture laden air gets into the wall, and it will with any house (there's your second law...) as the air warms up, the relative humidity of that air goes down.  Another way of saying that is, the ability of that incoming air to carry water vapor, increases as it warms up.  As a direct consequence of that, the water vapor will not condense in the wall. 

By applying a slight vacuum to the house, we insure that it is cold air that comes in, and gets warmed. 

The incoming air in fact, gains more and more ability to pick up water, and will actually dry a damp wall out.  Warmer air can hold more moisture than colder air.  That's why they call it relative  humidity.

Now let's imagine the other scenario.  Instead of a slight vacuum, the house is slightly pressurized.  Now, warm moist air from the interior will be pushed out through the walls (in all houses, there's that entropy problem again, just depends on how much/how fast).  It's still cold outside.  As the warm moist air gradually cools, its relative humidity goes up.  It becomes less and less able to hold the water vapor as vapor.  It becomes more and more likely to drop below the dew point and allow the moisture to condense on the nearest available object, surface or substance, often the plywood sheathing. 

With a big temperature delta, this is virtually guaranteed to cause moisture to condense inside the wall where it will do the most harm.

In a conventionally built house, it's luck of the draw whether you get negative or positive pressure.  Many have intermittent negative pressure because they have fuel burning appliances like gas furnaces and wood stoves.  So long as the device is running (pumping inside air out through the chimney), you can get significant vacuum build up.  Some houses, you can even experience whooshing noises if you open a window.  But when the device turns off, then the vacuum drops and the house may build up pressure in certain areas, depending on wind direction, wind speed, etc.  If you have electric heat, you don't get the benefit of this vacuum, and are more likely to have moisture problems from water vapor condensing in the walls.

I eliminated the intermittent large vacuum caused by the furnace (because I didn't need one anyway) by using a direct vent gas fire place in the Ontario house #1.  And I used a small muffin fan that draws less than 10 watts to move 20 CFM, for a house with an upstairs volume of 12,000 cubic feet.

If you run that 24/7 for a year, at .09 per kwh, that's 87 kilowatt hours, or about eight bucks worth of electricity to keep your house from getting moisture damage in the walls, and feeling perfectly fresh all the time.  Cheap insurance in my book.

So, when you say, "moisture control is not a big issue when the house can breath", how much breathing are we talking?

What sort of construction techniques gives you that?

To answer another question, I had several inspection ports that I built in to check for moisture issues periodically.  Nothing ever turned up.  Sadly, I only got to live in the house a few years before being forced to move for school and job reasons.

Thanks in advance,

troy
 
                        
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Location: Iowa, border of regions 5 and 6
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When I hear about "houses needing to breath", I remember to something that I heard over and over again in my Home Energy Rating System (HERS) training: Houses don't need to breath, people do.  The biggest offenders are houses with crawl spaces.  Until recently, crawl spaces were built with vents to "allow the house to breath."  Research in the last few years have shown that houses with vented crawlspaces have significantly higher levels of mold, rot, and internal air quality problems.  Houses built with sealed crawlspaces experienced none of these problems.

While I like the idea of using the small fan to continually promote air changes, I'd have to wonder if you're getting sufficient fresh air without having a system designed to bring in fresh air.  The only way you're going to know is if you pay an HERS rater to do a fan door test on your house.
 
Troy Rhodes
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For new construction, blower door testing is valuable to determine fairly exactly, what your air change rate is.  It's typically a few hundred dollars and might make excellent sales fodder if you ever have to sell the house.  Particularly if you can produce bills/evidence of ridiculously low energy costs.  The marketing of residential housing is about to undergo a major sea change with a lot of emphasis on energy costs.

In my current house, it is virtually impossible to get a retrofit of an old farm house sealed too tight, so I have no worries about fresh air.  And unlike the first house, this one uses a wood burning stove, and a biodiesel oil stove, both of which induce a vacuum and promote plenty of air exchange.

Finest regards,

troy
 
                                
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Hi Troy, I think where we are missing each other here, is you talking about improved modern building and I was talking about natural building materials-natural building seams to be a big part of this forum. Sorry if there was a misunderstanding. I've done conventional construction for 25 years and am only now seeing it's failure. The more I read about natural, breathable material, the more I realize why conventional and modern conventional is failing. Natural material can last 100's of years before failing, modern materials can fail in less than 10 years and then the "design theory" goes out the window. I've come to feel a house should last and be healthy for a lot longer than 30 years. As i 've said  this natural building is fairly new to me and has really opened my eyes to failed technologies- one's I've profited off for a quarter century. As for Air pressure, temp and humidity changes you mention in your last post to me. I totally agree with you in theory. The problem is the theory does not meet reality. It may work find if the air flow was always horizontal, but in a wall (especially those that are designed to prevent airflow) this may not be the case. I can see a uniform change in temp and humidity and you know what that means? Seriously, I say this because I've been in soooo many places that where supposed to be properly "sealed" and proper "airflow", but there  always was moisture and mold problems and it seamed to be the more they sealed , the worst the problem. It's just crazy how moisture would condense in the most unlikely of places.

just my thoughts and observations and nothing else

cheers
glen
 
Troy Rhodes
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Dear Castlerock,

I always appreciate being educated with something new as well.

what would be your dream house in a northern climate like michigan?  What would be the building material and construction method of choice to provide excellent long term durability with respect to moisture?

What sort of energy/thermal performance would you expect?

Thanks in advance.

troy
 
                                                                    
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Location: Nashville, Tennessee, USA
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Spray on urethane foam is an amazing insulator.  It seals the house from air flow and has great insulating properties.

I know it is not a naturally occurring material but it will save a lot of fuel.

It is about $1.00 per board foot installed. 

Local vendors here are recommending a 2" thick application.


 
Troy Rhodes
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Spray on urethane (not counting the obscure phenolic products) has virtually the highest installed functional r-value.  About 6.8 or 6.9.  It's expensive though.  And there's no do-it-yourself option.

If contractors are recommending 2", that's only r-14,not counting the framing/thermal bridging, which will bring that number down significantly.  Interestingly, the reason it looks so fantastic as an insulator is that the "normal" fiberglass insulation so grossly underperforms compared to it's stated r-value.  So the urethane provides a true r-14, while the fiberglass is just whistling dixie when they state r-12 or r-14 for a 3.5" wall thickness.

In Nashville I wouldn't go under r-30, so that's almost 5 inches of urethane.  They'll think you're crazy, but when fuel costs migrate up to double to quadruple the current levels, you'll look like a genius.

I think I could achieve the same thermal performance with cellulose at lower cost, and it's recycled newsprint.

The two main drawbacks with cellulose are:

1.  thick walls (although no thicker than the equivalent fiberglass insulated wall.
2.  you have to blow it, let it settle 6 months, and blow it again.  If you have a high pressure dense pack machine, ignore that.  It can settle 20% with a "normal" blower.

Finest regards,

troy
 
                                
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solarguy2003 wrote:
Dear Castlerock,

I always appreciate being educated with something new as well.

what would be your dream house in a northern climate like michigan?  What would be the building material and construction method of choice to provide excellent long term durability with respect to moisture?

What sort of energy/thermal performance would you expect?

Thanks in advance.

troy


Well, I'm in the process of learning and building. My land is located 2 hours north of Toronto, So it is as cold, if not colder than Michigan. It will be a timber frame house with cordwood and some cob infill. Will be bermed on the north and part east and west sides, have a earth roof and maybe an earthern floor, some passive solar heating and a masonry stove and much more. So my plan is to use  multiple methods to solve the problems of heating, cooling, insulation, breathing and moisture to hopefully build an efficient, comfortable and most importantly a healthy home.
I was just this weekend, referred to a neighbor who build a cordwood house 25 years ago. Lucky for me he was only 400 meters from my lot, I didn't even know he was there. Spent time twice this weekend talking to him about his experience building and living in a cordwood house.It was built on a floating slab  even though we have a deep frost line. The slab and cordwood wall have little to no cracks that I can see., even after 25 years and the cordwood is load bearing .The cordwood and mortar are also in almost like new condition. I was told they had no issues with warmth, drafts or dampness.. Their floor was a bit cold has they only put down 1" of insulation under the slab and decided on a flagstone floor. I'm looking forward to going back and discussing it more and can't wait to go there on a -30 day in the winter to see for myself
 
Troy Rhodes
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Excellent,

Keep us posted.  There is no "one size fits all" solution to our impending mess.

Finest regards,

troy
 
                      
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I would thin that having all the outside walls as well as the attic floor sprayed with at least 4" of foam would do the trick. That would cut air infiltration down to nil. Just a thought....
 
patrick campbell
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Sorry this is very old. Wonder if I can still ask, what your heat loss numbers are/were like?
How did you heat it?

We are looking to build a new home here in VT, and I am trying to wrap my head around how to do this so it is very efficient without causing the price to skyrocket!

With a full 2 story building and unused attic, I think going R60 in the attic should be easy enough by blowing in cellulose. Default specs on this home are R50 cellulose in the attic already.

Walls can be R40ish with offset double 2x4's with dense pack cellulose (~R40)

The basement is where I am not sure. I have seen suggestions to put rigid board under the foundation and basement walls, but have also heard of people just insulating the ceiling (floor joists of 1st floor), then basically leaving the basement unconditioned otherwise. The stock specs of the home call for 3" Thermax, which is ~R20. Prefer not to use spray foam whenever possible. Windows will be tricky also, as they seem to be able to add a lot of cost. Luckily, the home has great southern exposure.

One of things I was hoping to do was basically "steal" money from our HVAC budget and give it to insulation budget, and then be able to heat the home with 1 well placed Rinnai unit (their biggest one is about 38k btu - cost $1300), however it is only 83% AFUE, and then doing an on demand HWH, or .82 EF tank heater (Both about $1300 also).





 
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