Image Credit: buildABILITY Corporation
更多绿色建筑新闻
In Canada, private and public interests are working on a common problem: How to build net-zero energy housing that average homebuyers can afford.
Asked by officials in the government’s ecoEnergy Innovation Initiative for some new ideas on how to encourage energy efficient building, a company called buildABILITY Corp. put together a program in which five separate builders were invited to tackle the net-zero problem in whatever way they chose. As a result, single-family homes and condominiums are going up in five cities in four provinces as builders work with their own consultants to produce affordable net-zero energy houses in their respective markets.
Natural Resources Canada chipped in $2 million from the national $278 million ecoEnergy program. (All costs in this article are in Canadian dollars.)
Owens Corning Canada provided insulation products for free, and builders themselves came up with in-kind contributions that equaled the government’s ante, says buildABILITY president Michael Lio. The net-zero houses, all of which must be completed by next March, will be sold privately after the government double-checks to make sure they really will produce as much energy as they use.
The larger goal of the Owens Corning Net Zero Housing Community Project is to help production builders figure out how net-zero building practices can become part of their regular repertoires.
“We’ve been talking about it for a long time,” Lio said recently. “There have been lots of net-zero buildings that have been constructed both in the U.S. and in Canada, but there haven’t been many activities that focused on production builders, and even fewer on affordability. So at the heart of this project is to work with large production tract builders to bring them to net-zero and have them change net-zero so it’s more affordable for their customers, to simplify it and drop it into their assembly-line processes.”
Builders find common ground
建筑商正在独立工作。没有中央机构指导他们的工作，也没有必须遵循的共同脚本。Lio说，即便如此，建筑商还是采用了非常相似的方法。他说：“这些技术已经脱离了架子，非常易于使用。”
一些共同的建筑特征：
- Grid-tied photovoltaic systems for on-site renewable energy, with arrays averaging about 10 kilowatts.
- Exterior walls with R-values between 38 and 44. Wood-framed walls have cavity insulation of fiberglass batts and an exterior wrap of extruded polystyrene rigid insulation between 2 and 3 inches thick.
- 用鼓风机门测量的气密度为每小时1.5个空气变化，或较低的压力差为50 pascals。
- 三窗格窗口。
- Although some builders have chosen small-output furnaces, many others are using cold-climate air-source heat pumps.
- Heat pump water heaters.
- 内部聚乙烯蒸气屏障。
- Attics insulated with batts or blown in fiberglass to a range of R-50 to R-70. Roof framing consists of raised-heel trusses that allow extra insulation above perimeter walls.
Lio says the units have fairly small heating loads (most of the projects are located in Climate Zone 6). Half the 10 kW output of the PV arrays are on average used for base electric loads, Lio says, with one quarter devoted to space heating and the balance to domestic hot water.
Builders will sell the houses at market rates, Lio says, but because of program restraints they won’t be allowed to make a profit on building components that contribute to net-zero operation.
建筑成本相似
A total of 26 housing units are underway, ranging from one-bedroom condos to single-family houses. Floor areas run from 750 to 3,000 square feet. They’re being constructed in Laval, Quebec; the Ottawa suburb of Kanata; Calgary, Alberta; Halifax, Nova Scotia; and Guelph, Ontario, just to the west of Toronto. Lio says land prices vary widely, but construction costs are similar across the country. Single-family houses will probably be listed in the $500,000 range.
Lio说，在单户家庭上获得Net-Zero的增量成本似乎是60,000至80,000美元，比传统房屋的成本高12％至16％。Lio说，现在知道加拿大购房者是否愿意付款还为时过早。
Lio说：“我认为，作为一项全面的市场计划，我们真的很早。”“我怀疑会有一些购房者关注创新，他们想成为第一个采用特定技术并肯定会购买这些房屋的人。
“我们在价格出现剧烈波动of these systems, particularly on-site generation, and as some of these systems become even more affordable and builders start to adopt the technology in volume, then it would be appropriate to have a conversation about what the market would bear. Right now, it’s conjecture. Prices are high, numbers are low, and it’s really unfair to talk about would someone be willing to dish out $80,000.”
Building on a Canadian tradition
Canada has a long history of high-performance building and introduced itsR-2000程序在1980年代早期。利奥指出,斯坦dards typically become more demanding as time passes.
他说：“ R-2000在许多净零房屋的跳板上。”“ R-2000是一种能源标准，但不包括现场生成。这些零净房屋不仅展示了R-2000标准中嵌入的新型能源效率类型，而且还采用了下一个飞跃并嵌入无位置可再生能源。
“That’s the real difference,” he adds. “It’s a continuum. We’ve been at it for a long time and we’ve made lot of mistakes along the way, but it’s pretty obvious that there’s this continuum and these programs that are voluntary eventually become the stuff of code minimums.”
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14 Comments
Wall R value
“ R值在38到44中的外墙。木结构的墙壁具有玻璃纤维板的腔体和挤压聚苯乙烯刚性隔热材料在2到3英寸之间的外部包裹。”
How does a fiberglass batt plus 2-3 inches of XPS yield between 38 and 44?
Response to Reid Baldwin
里德，
Your question has several possible answers.
Let's do the math: An R-38 wall with R-15 of exterior foam has R-23 of insulation that is not foam. If the wall is framed with 2x6s, then you can put R-20 of fluffy insulation between the studs. The rest of the insulation (R-3) would need to come from insulated siding (insulated vinyl, for example) or some combination of interior finish materials and air films. Otherwise, the walls would need to be framed with 2x8s.
An R-44 wall with R-15 exterior foam has R-29 of insulation that is not foam. If the wall is framed with 2x8s, there is enough room for R-26 or R-27 of fluffy insulation between the studs. The rest of the insulation (R-2 or R-3) would need to come from insulated siding or some combination of interior finish materials and air films.
在大多数项目所在的气候区域中，至少36％的R值需要来自外部刚性泡沫（如果使用外部刚性泡沫）。因此，R-15外泡沫将用于总R-41.6的墙壁。如果您的目标是R-44，R-15泡沫就会变得边缘。
我想不出任何简单的方法使这些墙与R-10外部刚性泡沫一起使用，除非螺柱之间安装了喷雾泡沫绝缘材料。
还有另一种可能性：这些加拿大建筑商正在使用Polyiso，并假设2英寸的Polyiso具有R-12的R值为R-12，而3英寸的Polyiso的R值为R-12。这就是标签所说的，所以我可以理解这个假设 - 但是Polyiso在寒冷的温度下表现不佳，因此对于加拿大外部刚性泡沫来说，这不是一个不错的选择。
Are the costs referenced in $US or $CAN?
Are the costs referenced in $US or $CAN?
Wall R value
感谢您的回应马丁。
我在整个壁r值方面考虑，但它们可能正在报告标称R值。您的分析表明，名义R值至少可以接近所述内容。
Since they are using interior polyethylene vapor barriers in combination with exterior XPS foam, I suspect they are not reading GBA.
Response to Reid Baldwin
里德，
I agree with you completely on the issue of exterior rigid foam plus interior polyethylene. Even if those Canadian designers don't want to subscribe to GBA because of the high cost (in US dollars) of subscribing, they could learn a lot from our free articles.
Et si quelques-un de nos amis canadiens veulent poser des questions en français -- c'est possible aussi. Nous répondrons.
Costs
John,
Costs are in Canadian dollars.
有人说“免费的棉花糖”？
Years of consistent funding for building energy conservation since the 1970's by both GOP and Dems has fostered an incredibly rich discussion south of the 49th. I'm jealous and the Yanks should be proud of this achievement; pragmatism over partisan dogma - something the Cons here can't get past.
GBA是人们可能喜欢讨厌的视觉（FHB）和精心策划的内容的结果，但最终通常会呈现出有关建筑科学和务实施工技术的文章的技术鸿沟。
Many Canadian contractors still don't know how to dense pack cellulose properly and you can see from the article above that we eat free cotton candy without question like a polite Canadian! It's quite possible that some of the builders and some of the designers involved in the NetZero projects above have never heard of the Pretty Good House or GBA for that matter. In the last decade, Canadians have slipped back to the 1990s and we're a fragmented group spread over a vast area of land.
正是由于这个原因，我想打电话给GBA帮助加拿大人看到灯光，让我们首先将斯科特·吉布森（Scott Gibson）指定为荣誉加拿大人。
poly and exterior insulating sheathing
The question of whether low perm insulating sheathings cause moisture problems has been recently addressed in a comprehensive study by the National Research Council of Canada's Code Centre. Dr. Hamid Saber has shown that the sheathing's R-value is the key factor that influences interstitial moisture and not its permeability. (Look for a possible code change that relaxes the current rules). The wall assemblies for these net zero homes meet the outboard/inboard ratio requirements of the Code's in each of their four provinces. Tens of thousands of houses have been built across Canada with exterior insulating sheathings (XPS) and poly without consequence.
回应迈克尔·利奥
Michael,
谢谢提供信息;我很感激。在搜索更多信息时，我发现Saber博士的名字是Hamed，而不是Hamid。我找到了一个相关的网页：
http://www.nrc-cnrc.gc.ca/ci-ic/article/v18n2-10
If anyone has a link to a report on Dr. Hamed Saber's study, please share it.
Found a paper by Hamed Saber
Here is a link to one of Hamed Saber's papers -- but it's one that makes no mention of polyethylene:
“具有不同外部绝缘的木框壁系统中凝结和霉菌生长的风险。”
Dr. Saber wrote, "The results showed that decreasing the air leakage rate resulted in lower risk of condensation and mould growth. The values for the overall average mould index of walls configured with structural sheathing are lower than that of walls configured without structural sheathing. St John’s appears to have the most severe climate in comparison to the other three locations investigated (Ottawa, Edmonton, and Vancouver); the greatest values of the overall average mould index of the wall configurations amongst the four locations occurred in this location."
It wasn't about polyethylene (response to Martin, #10)
The point of that paper was to study what happens if they adjust the required maximum vapor permeance was relax from about 1 US perm to about 5 US perms. Ergo, no mention of polyethylene, which is two orders of magnitude more vapor tight than 5 perms, which is basically the difference between a minimalist Class-II vapor retarder and standard latex paint. It's spelled out in the first paragraph of the Abstract:
"The work originated from a Code Change Request “CCR-802” in which it was suggested that the Water Vapour Permeance (WVP) limit be raised from 60 to 300 ng/(Pa•s•m²) while leaving the limit for air leakage of building envelope materials unchanged at 0.1 L/(s•m²) at a pressure difference of 75 Pa. "
One US perm= 57.2 ng/(Pa•s•m²), so 300 ng/(Pa•s•m²) would be 5.24 US perms- roughly the vapor permeance of a single layer of interior latex primer.
What the paper reports is that with only 5 perms on the interior, a 2x6 R19 wall with no exterior foam has significantly higher mold risk than the same wall with R4 foam on the exterior in a number of climate zones. (We kinda knew this, but they quantified it.)
Even though Canadian code only requires a minimal class-II vapor retarder as the interior side vapor barrier, 4 or 6 mil polyethylene is cheap & ubiquitous, and has become the industry standard despite being an order of magnitude tighter (for both good and ill.) 2-mil nylon meets code as long as the air next to the sheet is reasonably dry (and becomes more vapor open at high humidity, a desirable feature) but it costs twice as much as 6 mil poly.
Response to Dana Dorsett
Dana,
My reference to polyethylene was in response to Michael Lio's comment that "Tens of thousands of houses have been built across Canada with exterior insulating sheathings (XPS) and poly without consequence."
我同意Lio的陈述，但我想知道Hamed Saber博士是否已经研究了具有外部刚性泡沫和内部聚乙烯墙壁的风险问题。迈克尔·利奥（Michael Lio）暗示，萨伯（Saber）已经对该问题进行了研究，但我尚未找到指向直接解决该问题的论文的链接。
内部聚乙烯
I have yet to ever see a problem here in Climate zone 6 with interior poly and exterior rigid insulation. Never not once! I have taken apart lots of these wall assemblies years later and have never seen any issue of mold or significant condensation.
In theory the double vapor barrier sounds scary enough but in real life in cold climates I am not so convinced!
flashing
Kye,
The usual argument about double vapor barriers is that if water leaks in somehow (e.g. a bad flashing job), it will accumulate without any way to dry. Perhaps Canadians do a better job of flashing things well than Americans do.
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