New home questions
I plan on retiring to BC in a few years and building ” a pretty good home” . I have been reading almost everything on the GBA web site, very informative. Really appreciate all the blogs by Martin and all the others .
I have a few questions : 1) the square footage of glass to total square footage of the home: in my home (1600 sq’ bungalow ) the actual windows :182 sq ‘ (11.49%) actual glass only:( 115 sq’ ( 7.2 % of floor area). So when it is recommended to have for example window to floor ratio 10%, what are we talking here , the actual or the total window size ? A big difference 11.5 % vs 7.2 % !
2 )I did a calculation of a hypothetical 1400 sq ‘ bungalow heat loss ceiling design temperature 25 degree f, r value 70 (u.0142),delta t = 40 , comes to 994 btu / hr.
Then I did a slab heat loss ( assuming FPSF) ground temp 50 degree f, delta t 20 , R10 (u.1) and I came up with 2800 btu/ hr. Does that seem right , almost 3x the heat loss thru the slab ?
3）正在考虑使用Lunos E2 HRV以易于安装（没有笨重的通风管运行，尤其是没有地下室来运行管道），这项工作是否可以使湿度保持在开放式概念平房中的湿度（2成人）的任何人，任何人这些单元有任何经验吗？
4) About a year ago there was an article on vacuum insulated glass being available in late 2014 , Ply Gem windows and Guardian Glass. Any word on the latest development of these?
感谢您的时间回答这些问题。
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Replies
The slab losses are way overstated unless the soil under the R10 foam is right at the water table, and highly conductive. In practice even in foggy-dew Vancouver the soil won't be that wet and there is substantial R-value to the soil.
No word on the new projections of when vacuum insulated glass hits the market. Ply Gem seems eerily quiet, as are the other vendors who were hot on the trail a few years back. As I understand it there are problems still to be solved surrounding the high mechanical stresses these windows see at high temperature differences between the interior & exterior panes due the expansion/contraction of the panes. Maybe that will be solved some day, but don't hold your breath.
Bert, BC just revised its building code last month to include new energy requirements - which among other things include the percentage of windows allowed. Here is a link you may find useful:
http://www.hpo.bc.ca/sites/www.hpo.bc.ca/files/files/download/guide/web_section_9.36_zone_4.pdf
Bert,
When people discuss glazing ratios, they are usually talking about square feet of glazing, not square feet of windows.
One online reference (http://www.rci-online.org/interface/2012-bes-marceau-hoffman.pdf) refers readers to "the definition of glazing found in ASHRAE 90.1."
Lunos ventilation fans work well, by all reports. If you are worried about the sufficiency of the ventilation, make sure that you install enough Lunos fans to meet the minimum ventilation requirements of ASHRAE 62.2. For more information, seeDesigning a Good Ventilation System.