GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

New home questions

matterbt | Posted in Energy Efficiency and Durability on

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) Am considering Lunos e2 hrv for ease of installation ( no bulky ventilation pipes to run especially not having a basement to run the ductwork in) Would this work for keeping the humidity in check in an open concept bungalow modest size (2 adults ) Anyone have any experience with these units?

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?

Thanks for your time on answering these questions.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Dana Dorsett | | #1

    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.

  2. Expert Member

    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:

  3. GBA Editor
    Martin Holladay | | #3

    When people discuss glazing ratios, they are usually talking about square feet of glazing, not square feet of windows.

    One online reference ( 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, see Designing a Good Ventilation System.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |