Efficient prefab?
 

I mentioned to a coworker that I was thinking about building a small, efficient house, and he brought up the topic of prefabricated houses. Viceroy is a company from Southern Ontario who can build houses here fairly inexpensively and very rapidly. All of Viceroy's houses seem to feature good Ar-insulated windows, 2x6 construction, and generally good attention to insulation and comfort.

Are there any companies out there shipping prefab houses that meet, or come relatively close to meeting, Passivhaus standards?

Viceroy doesn't give out free copies of their catalog, even online, but I did find one of their houses here:

Niagara

http://gastoninc.com/Blue/niag3.jpg

The above house is about the right size for me at the moment, at 624ft² on the outside (575ft² inside the exterior walls). It's not as well insulated as I'd like, but I like the layout. Most of the windows are facing the same direction, which should be south. It's very flexible, with an interior layout available for a one-floor or a two-floor variant. It can be built on a basement, or built above a finished lower floor with two additional bedrooms.

I would like to see it build above a garage. In the event that I should sell the house or have a large family, a detached garage could be built, and the lower floor converted to living space. That would make it a respectable 1248ft². Or maybe I'd just leave room to the side to double the square footage later.

I have a while to think about what kind of house I want to buy or build, but a prefab small house would be very attractive.

Prefab Passive Houses certainly are being made in Europe. They are trucked out to the site and assembled amazingly quickly. And yes, they meet Passive House standards.

If I'm not mistaken, they are out of one of the Scandinavian countries... Norway maybe?

I have seen a couple of documentaries that described the whole process.

This is really the kind of thing that would make a glorious dent in our crazy energy consuming ways.

I think you are on the right track, such a business may already exist. You might try sending some emails to some of the Passive House organizations (Passive House US & Passive House Canada), there's an excellent chance that they would know of the existance of such a biz.

Also, I think there may be some leads here.

Good luck, you're definitely moving in the right direction.

-AC_Hacker

They do make some green prefabs.. Found a story in the NYT..
Posting - Designed, Delivered and Sealed - NYTimes.com

Here's the builder site:
New World Home

Xringer, those are modular homes, which I hadn't even thought about. Modular homes are built in a factory and trucked to the site, while prefab homes just have the framing and some subassemblies done in a factory and are assembled on site.

Due to shipping constraints, the New World homes are 15.75' wide. Hence the olde-fashioned styling, and the large percentage of floorspace spent on hallways. Here's a link to the New World Homes floorplans: http://blog.newworldhome.com/wp-cont...Small_1026.pdf

AC_Hacker, thanks for the link. I'm sure there's lots of good reading out there, but the signal to noise ratio is a bit low.

I doubt that this meets your needs but it is certainly an interesting type of prefab home.

Cabins | Monolithic

I agree, motivation does get overestimated.

-AC_Hacker

Passive House - First Steps...
 

I came across this little ruby while I was wandering about on the web.


Although it's intended audience is European, and the examples are aimed at that audience, there are some great ideas here. It would be very useful if the above chart could be adapted to N. America.

But even so, it is very interesting the difference that an 80% Heat Recovery Ventillator makes in wall thickness vs. a 60% HRV.

-AC_Hacker

In order to get to passivhaus levels you will need 16" - 18" walls (assuming you use cellulose) with no thermal bridging at all. I doubt you will find exactly what you want already set up for you but it wouldn't be too hard to adapt something to meet passive standards.

I did find out that at least there is a firm in Canada that designs Passive Houses, and they have certified builders, also in Canada, with whom they have co-ordinated working relations who are qualified to properly execute the designs. They are also trying to get Passive House qualified builders in the US.

From what I have been able to find out, there are stringent techniques used to achieve an air-tight house that go way beyond what would be considered normal building practices. And then there are the techniques used to get the required insulation levels. So among areas of focus are:

• superinsulation
• airtight construction
• mechanical heat recovering ventilation
• high performance doors and windows
• window placement to minimize heat loss & benefit from solar gain

High performance doors and windows go considerably beyond what is generally available in the US.

I did find that Certified Passive House Consultant Trainings are taking place...

...and that they are screening for serious qualified people for these trainings...

...at first I thought it was a trade association thing, closing ranks, but then I came across this link to passive house related building practices, and I remembered that what is now known as Passive House actually started with the Super Insulation initiative and also combined the Passive Solar ideas, and was then picked up by the Germans who refined the ideas and devised a way to generalize construction for any building site and climate. (by the way, the listed 'best practices' manuals are not all currently available, but if you make use of archive.org, you can still find them.)

So I think that what is going on is that Passive House organizations world wide are making a very steep claim, namely that energy use will be 10% of 'normal, well-insulated homes'... and they want to make sure that homes that carry the Passive House name actually achieve that goal.

From what I have read, trying to retrofit a house to Passive House standards is simply not possible, but it is possible (not easy) to get to 20% energy use of 'normal, well-insulated homes'.

I know that I would be quite pleased to get even close to that.

So, "...wouldn't be hard...", wouldn't be too right. Meeting Passive House standards is a very high bar.

-AC_Hacker

Yeah in order to reach the level of tightness and the lack of thermal bridging found in a passivehaus you really need new construction. To meet the standard you need no more than .6 ACH @ 50, which is pretty hard to do even in new construction much less in a retrofit. Although I think that you could get lower than 20% with a retrofit. I'm buying a house so we'll see, won't we?

Near Passive House Retrofit...
 

Certainly a very worthy goal.

I hope you start a well-documented thread, I think there will be great interest in your efforts.

Best Luck,

-AC_Hacker

A very worthy goal.

I hope you start a new thread on your project, I think there would be great interest in this.

Best Regards,

-AC_Hacker

With some spray foam insulations claiming twice the stabilized R-value of cellulose, it might be doable with 8-9" walls with no thermal bridging, e.g. with steel studs. I wonder, would the increased cost of spray foam insulation be made up for by the savings in lumber, framing labor, window and door trim, and per-square-foot taxes?

Vacuum insulated triple glazing and 18" walls would be nice, but I view them as very expensive toys. I'm inclined to go with a very efficient, 2x6-framed, well sealed house with ventilation heat recovery and good, south-facing double-pane windows. Who knows; it might be passive nine months out of the year, and pretty close in August, January, and February.

As the price of heating and cooling get higher in the coming years, I'm trying to
imagine what people will do to retrofit their 2x4 walls and lossy windows..

Adding two or four inches to the thickness of their walls and installing another window
on the inside, sitting in a frame built into their new layer of interior wall..

The big problem with the spray foam (aside from the stupid cost) is that as the gasses escape over time the R value will decrease. Basically the best you can get from air is R 4. So these R 7 foams will slowly make their way down to to R 4 over the course of 15 - 20 years. They are also pretty nasty, high embodied energy, they give off terribly toxic fumes when burned and they drive moisture into the framing lumber. Cellulose draws moisture away from the lumber. It's also made form recycled news papers. There is no end to the benefits of cellulose. The only thing that foam has on it is R value. Just make you wall a little thicker. It'll be greener in every sense of the word. The indoor air quality will be much better. It will cost less. You can't go wrong.

Stick built with cellulose insulation is going to be the best value. Add a nonloadbearing inner wall framed in 2x3's. Take time to caulk all the cracks, it makes a big difference.

Cellulose will settle over time, leave access panels at the top of the ceiling to add cellulose insulation every year until it stops settling.

If you dense pack it properly this will never happen. The 3.5 lbs./ft. of proper dense packing is so far beyond settled density that settling is not even remotely possible. If you leave access to the cavity you will invariable also leave air leaks that will cost you a ton in convective heat loss.

How do you dense pack, tamp it down with a 2x4? What if you don't have access from above, how do you get the top part packed down?

Just google dense pack cellulose. I have also seen some good videos on youtube.You can actually insert the tube into the middle of a cavity and dense pack the top down. When it's dense packed it will actually hold in place while you pack beneath it. The only way settling will occur is if it's done improperly. This doesn't happen in new construction because the wall get's packed before the sheet rock goes up so you can actually test all of the little nooks and crannies. There is no tamping involved. It's a combination of the pressure from the blower, adjusting the cellulose/air flow, using a smaller tube and technique.

Yes I plan to document it thoroughly. I need a camera though. When the Mrs. moved out she took the camera along with everything else. I see that the biggest lack in energy efficient knowledge is in the field of tightening up old houses. On Saturday I went to a house that has already had 3 energy audits. I guess the work they did made a little difference. Not much though. I still managed to measure air pouring out of a recessed light at 2 meters/second. I couldn't even get the house to 50 pascals with the blower door. The home owner was all gung ho about installing insulation but it will do him little good when there is a hole in his basement going right into his unconditioned crawl space. o.0
You can have a 24" spray foam wall that will do you nothing if your house moves that much air. In new construction (what we hear about most) making things air tight is pretty easy. Still getting to passivehaus levels (.6 ACH @ 50) is very difficult. Even getting to 1 is pretty hard. You need to put the blower door in backwards, pressurize the house and walk around with a smoke pen to find all of the air leaks. For an older house you could just pressurize and set up a fog machine to see where air is moving with some people on the outside also.

There are some good points here, but also a few things that are not universal.

Foam is rated based on its "stabilized R-Value". The R-value drops over the first two years or so, but then plateaus after all the bubbles that are going to collapse have done so. The R-value would be higher than advertized during the first two years. Of course, fiberglass and cellulose settle and lose R-value over time too, so it's smart to compare aged to aged.

Unlike fibrous insulations, the R-value of foam is not affected by wind. It forms a very durable barrier to air and vapor. The fact that it repels water while cellulose absorbs it seems more like a bonus than a drawback.

They do burn energetically, but they contain fire retardants, and meet fire code when installed behind drywall. Good enough for me. And yes, in the event of a structure fire, I'll pop on a charcoal respirator.

Different blowing agents are available. The used to use CFC's. R134a is one option, which is ironic considering its GWP. Other foams use various inerts, including CO2. To tell a contractor to spray foam, without specifying a specific foam and friendly blowing agent, would be crazy. However, whether adequate performance can be derived from, say, a CO2-blown foam remains to be seen.

The Rth of air at STP is about R-5.5 per inch, so that's the best you can do with tiny bubbles of immobile air.

Dense pack will never loose R value as it's beyond settled density. Loose fill will though. There are two measurements for it's R. One is new and one is settled. These foams are showing to loose considerable R value over time. Much lower than their spec. The gasses continue to escape into the air. It just takes some time. Maybe 20 or more years. But most people building these days only think about the next decade at most. The hygroscopic value of cellulose is very good. It moisture levels. It doesn't absorb it and hold it unless it's soaking wet. It will facilitate drying of all of the structure. The foam rejects moisture forcing it into the lumber. This is a great plan for rot. In such a house humidity will need to be carefully controlled and kept to a minimum.

Rearding foam vs cellulose, I started my house insulation with foam because at the time the other choice was fiberglass and I wanted much higher R-value per inch. Even though foam was more expensive, it seemed like a good choice. Now that I have done most of my house, and the results are encouraging, were I to do it again, I would go with cellulose... maybe with a foam skin against the outside wall to stop the leaks, then dense pack in the remaining space (I increased the space to 6 inches).

I really like what I have read from eco-savvy Europeans... they seem to have a more thoroughly-internalized understanding of embodied energy, and carbon sequestration. Here in USA, 50% don't believe in evolution (for them personally, it apparently didn't happen) and about the same number doubt that global warming is occurring, or that it is a concern. That's pretty dismal... something crucial has failed in our society.

So, I think it is easier for Europeans to encompass the many aspects of eco-decisions, such as what to use for insulation, and to see that R-value alone is not enough to make a decision... there is also embodied energy and sequestration of carbon. I really think that when all the factors are weighed, better choices can be made.

Wow, S-F... you have your own blower door?

You've been holding out on us. Got any pix of it?

BTW, regarding camera, I don't know if you are a thrift store junkie like I am, but very good 4 and 5 Meg still cams are pouring in to the Goodwills all across our fair country. Be sure to take some good batteries with you and test them out before you buy.

I picked up several and gave them to friends who hadn't gone digital yet.

I was paying $40, now they are typically $10 to $15.

-AC_Hacker

I rent a blower door when ever I need one. I admit it would be pretty cool to have one but I can't justify the $2,700 cost. I rent them just up the road a mile. The place is right across the street from where I'm moving. That's also where I get spray foam and other materials. But I'll definitely document the leak testing thoroughly when I do it.
Thanks for the tip on the thrift store cameras. I never would have thought of that. Unfortunately (fortunately?) where I live there is an abundance of thrifty people so the goodwill is usually bone dry. I'll have to go up the river to one of the other towns or troll some thrift stores next time I'm in Boston.

An interesting point: I was recently talking to some German passivehaus folks and they were saying that foam is better because there is a potential for the cellulose to have a negative impact on the indoor air quality with airborne particulate matter in a negative pressure situation. Negative pressure is a little more feasible in a house with electric range and direct vent DHW and heat. Seems nuts to me as the foam at best can't be doing anything to help the air quality (which cellulose can by way of moisture mitigation) and very probably is off gassing some things I don't want to breathe. I'd rather wrap news papers around my head than spray foam all over it.

EcoRenovator's heating degree days...
 

Here are some heating degree days for some of the many past and present EcoRenovator posters.

I used this URL to get 5-year average degree day info.

I tried to get a variety of locations, and in most cases I needed both a city and state (or country). In a few cases, I just guessed.

higgy
Winnipeg, Manitoba
10422

Maxis
Riga, Latvia_
7800

Daox
Germantown, WI
7138

Piwoslaw
Warsaw, Poland
6722

Xringer
Woburn, MA
6412

Big Al
Glasgow, Scotland
6319

osolemio
Copenhagen, Denmark
6230

TimJFowler
Santa Fe, NM
5755

AC_Hacker
Portland, Oregon
4576

Hugh Jim Bissel
Dallas, Texas
2244
?????????????????????????????????????????????????? ?????
if you are not included on the list, not to worry, I was trying for a variety of locations. You can go to the degree-day URL, find your average degree day, and cross check on the chart to find your own wall thickness.
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Then I took a look at this table which showed Passive House wall thicknesses for various locations in Europe.


I then found the heating degree days for each location mentioned on the chart, and did a point scatter of degree days vs wall thickness and did multiple curve fits on this data scatter and found that a linear fit was not perfect but still close enough to be very interesting.


So I used the formula from that linear fit, converted all cm wall thicknesses to inch wall thicknesses, and Applied it to the EcoRenovator list to see what Passive House wall thickness would be about right for their location's heating degree day figure.


So this chart should give you a rough idea of how thick your Passive House wall thickness might need to be. This assumes that a HRV of certified 80% or better efficiency was used, and that Passive house standards of insulating and sealing, etc were adhered to.

Kind of interesting don't you think?

(NOTE: data error has been repaired)

-AC_Hacker

I'm surprised how good that linear fit is, considering all the factors that could skew it. HDD indicates how long * severe a winter is, but insulation thickness in a passivhaus with adequate thermal mass really only depends on the coldest week, and sunlight levels.

I see you have R=0.90. Can you get that higher by correcting the Moscow data point? (I assume that Moscow is colder than Brittany, else why would Napolean have run into trouble?)

There are many factors that could explain outlying data points. Passive house design takes many factors into account.

I did this work to suggest what wall thickness might be needed for various location's HDD, hoping that it could initiate further interest in Passive House design.

If this is useful to you, use it. If it is not useful to you, please disregard it.

-AC_Hacker

Passive House "Best Practices"
 

Some Passive House Power Point slides... a bit of overlap but good ideas..

Link 1

Link 2

-AC_Hacker

S-F,

Since you're contemplating a major insulation overhaul (Deep Energy Retrofit), I came across some really good sites that address just such a thing:

Deep Energy Reduction Retrofit with Passive House Tools

Remodel Project: Deep Energy Retrofit

Deep Energy Retrofit of a Sears Roebuck House

This is a Swiss outfit that specializes in air-tight layer construction. There are also some Youtube videos that could be helpful.

-AC_Hacker

You must have had it set to Moscow, OH, because Moscow RS (UUEE), at 56°N, had 8805 HDD (ref 65°F) last year. That reconciles nicely with the 20" of wall thickness.

56°N... that's awfully close to the arctic circle. It has to be tough to be passive when the sun is 10° above the horizon at noon on the solstice.

This is the data set I used:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>
Description:,"Fahrenheit-based 5-year-average (2006 to 2010) heating degree days for a base temperature of 65F"
Source:,"www.degreedays.net (using temperature data from www.wunderground.com)"
Accuracy:,"No problems detected"
Station:,"Airport: Moscow Vnukovo, RS (37.27E,55.65N)"
Station ID:,"UUWW"

,HDD
Jan,1517
Feb,1376
Mar,1072
Apr,663
May,325
Jun,160
Jul,97
Aug,134
Sep,353
Oct,694
Nov,979
Dec,1253
Total,8623 <===============
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>

...try something else.

-AC

The second-last data point here, the one that does not fit the curve, corresponds to Moscow and should have around 9000HDD, not 4500. I bet your correlation coefficient would go from "meh" to "aha!" if you were to correct that. That's all I'm getting at here.

NOTE: data error in post # 26 has been repaired

-AC_Hacker

The angle at which the sun's rays hit the window is much closer to perpendicular. But yes, the sun is above the horizon for no more than 6-7 hours, plus the rays of sunlight have to travel through a thicker layer of atmosphere. Here in Warsaw (52°N) the amount of energy from the sun in the winter is 4 times less than in the summer (~350 W/m2 vs ~1300 W/m2). I believe that passivhaus design for locations close to the polar circle is geared towards thermal mass, to hold as much of summer's/autumn's heat for as long as possible, and towards using heat produced by the inhabitants, cooking, and waste heat from electronics. "Don't unplug that wall wart or we'll freeze!"

Aha! An r-value (the correlation coefficient, not the insulation value) like that proves that Passivhaus wall thickness is in fact linear with annual HDD.

Looking at the third plot, I see I fall in with most of the rest of the EcoRenovators, around 6000HDD/yr. This suggests an insulation thickness of 14". Hmm, that's an awful lot.

AC_Hacker, you mentioned that you would do cellulose instead of foam if you could do it over again. Would you recommend cellulose over a CFC-free (e.g. CO2) blown foam as well?

Hah... I've been there.



Viceroy have sent me a pricelist and specification sheet for their houses... they also mentioned that their houses are well sealed, and many customers install a ventilation heat recovery system. I like everything I've seen about them so far, except the fact that new construction is a fair bit more expensive than buying used. But the opportunity to get the house I want, in the right location, sited correctly, is pretty compelling.

Just putting this out there:

You seem to be looking for something particular.

You give the word and I'll be there in 3 days with a 16 man framing crew to do your job for less than what you are looking at. And it will be done right.

PM me if you want.

There may be an increased cost in spray foam insulation if you use it but if you go with Structural Insulated Panels with new construction, you avoid the framing labor, get a thinner wall than using fiberglass or cellulose. Since it is rigid foam inside, you have a built-in vapor barrier and air sealing that is hard to mess up too. Doing a little reading to see if these can be bought thick and it seems Wikipedia mentions that they can be 12" thick. If the stuff is polystyrene, which I think is R-5 per inch, it would be about R-60, right? Since there is no framing members, no thermal bridge, you would just need to worry about the air sealing and thermal bridging of penetrations like doors and windows.

It was my impression after watching a television show on prefab houses about 5 years ago, Build one place, ship somewhere else and assemble. The show I was watching explained how instead of using nails and screws, attaching components with adhesives were used instead to speed up the process. I thought it was fascinating. I thought they used SIPs in the construction.

http://www.ecosteel.com/tech/insulatedpanels.pdf

EcoSteel offer a 4" structural insulated panel with R-14, and a 3" insulated panel with R-24. A 10" stack of SIP + IP + IP would have R-62, and a 13" stack would have R-86. As EcoSteel are happy to remind you, these are "whole wall performance" figures, including thermal bridging effects. So a 12" SIP would be a serious performer, perhaps even overkill for any application other than a northern Passivhaus.

Yes.

Fine Homebuilding mag from the early part of this year, has an article on foam + cellulose, and they even talk about the minimum foam thickness required to prevent condensation.

-AC_Hacker