Have you talked to some window manufacturers?

I've reached out to some window suppliers but haven't heard back - thought someone on this forum might have some experience of this. Getting to a USI of < 1.1 seems doable with triple pane windows, but can we also achieve the solar gain at these levels?

What is USI 1.1? What type of windows are you using (dbl hung, casement, etc)? What manufacturers are you looking at? What area of the country?

They are imperial u-values= about 0.19 for you yanks. Yes, it can be done.

@millworkman Thanks for chiming in - so the U value is the amount of heat lost and we've been told they are achievable with triple pane windows, but coupling this with solar gain seems to be harder. The way I've understood it is that these 2 things are inversely related.

So with low U values you achieve this with more glass (i.e. third pane) but that then reduces the solar gain .. I'm no physics person but is it because less UV light is coming through the thicker glass? Guessing to get higher solar gain you want less tinting? I might just be talking nonsense of course!

@toddinmn do you have insights into this solar gain - how is it achieved, special coatings?

The windows themselves are going to be casement type. We are based in Vancouver, Canada and I don't know the manufacturers out here I'm kind of relying on the window company.

Basically it is done with special Low-E coatings And where in The glass pack it is located but not proprietary to my knowledge. Most any company could make a window to achieve those numbers, but if might be Little more difficult for a wood window.

I think I would find the material you want , then sift through the different brands. Perhaps some others here know whats available in you market.

Can I ask what you are building and confirm that you are building in Vancouver? You say "based" in Vancouver - so just confirming.

The window spec you are looking for is significant overkill for your climate. I have a net zero energy house (ie solar output > energy for house), have a lower temp in the winter, and survive just fine on .27 and .28 windows (u value).

Triple pane windows are only cost effective in very cold climates. Vancouver is so warm that Canada has a climate zone built essentially for Vancouver (exaggeration). It has <3500 HDD. The average low in Jan is 37 degrees. OP - obviously you know this - just pointing it out in case others didn't.

Energy raters are great but this one might be great at spending other's money. But I realize Canada is way more aggressive than we are and Vancouver is a very expensive place to build anyway. Just go in eye's wide open.

95% of British Columbia's electricity is hydroelectric.

Cardinal has a bunch of information on their site to where you can start designing the right combination of glass coatings.

https://www.cardinalcorp.com/technology/reference/loe-performance-stats/

@Windows on Washington Ltd - thanks that's very useful - so it at least appears there is a way to achieve the SHGC, I'll reach out the window people see what they say.

@David Cary We are in Vancouver (main and 38th). The reason why we are going down this route is the following .. Due to the City of Vancouver GHG limits for new houses (3 tons/yr) we are hitting that limit as the gas radiant heating is around 2.7tons. So the energy advisor is saying we need electric domestic hot water. But that then pushes us to the edge of the 200 amps that BCHydro provide for a regular house (we are also building a laneway which shares the 200 amps)

Another 200 amps from BCHydro is 25-30k. So we are exploring other options. We were given the following advice:

"It’s possible to meet the GHG cap with the following (in the main house only):

• Triple glazed windows – USI 1.1 or lower and SHGC (Solar Heat Gain Coefficient) between 0.25 and 0.35. South facing windows high SHCG 0.40
• Air tightness – 3.0 ACH or lower. You need to hire an insulator who has a proven track record in consistently achieving this level of air tightness.

Plus you need to choose 1 or 2 of the following (each of these have different levels of impact):

• Drain-water-heat-recovery – Add a drain-water-heat-recovery unit.
• On-demand hot water system (tankless).
• Remove skylight and skylight shaft.
• Remove gas fireplace (change to electric)
• Increase attic insulation to R60

Alternately:

• Further reduce the air tightness to below 2.5 ACH by creating ceiling service cavity below the air barrier (2x6 furring below trusses)."

So we think the most economic is triple glaze windows, air tightness, on demand water (gas) and more attic insulation. We are acutely aware of the additional costs, but what choice do we have the COV is really pushing the energy conservation agenda.

+1. Very intelligent window company there and some hyper performance products to be certain.

Ok - why the heck would you do gas heat with a GHG limit? You could do heat pump and hit that with single pane windows (not that you would do that).

Building gas radiant heat in a moderate climate with a tight house is ... I can't find an appropriate word. You are spending a lot of money on a system that barely works.

When I hear radiant (in the US), we are talking floor based heat. WIth a tight house, the floor will never feel hot. The floor gets to 80 degrees and shuts off because the house is too hot.

In a cold climate and a loose house, it feels fantastic and is worth the money.

ACH 3.0 is very easy to hit and matches better with modest double pane windows. 1.0 ACH would match with triple pane windows. Not that matching of anything is necessary but just best bang for buck. We have a 1.7 ACH and double pane (u-.27) windows.

Heat pump hot water?

Personally, I would rethink the gas radiant heat. I would ask, have you ever been in a modern house with low ACH and good insulation with gas radiant heat?

It sounds like there’s some confusion around U value vs SHGC.

U values refer to the amount of conductive heat that passes through the glass - if you press your hand against the window on a cold day does the glass feel cold? That’s conductive heat transfer. Lower U value means less heat is conducted through the glass. This is usually achieved with filling the space between the panes with a noble gas (argon or krypton generally.)

Solar Heat again Coefficient refers to how much heat is radiating through the window. If you’ve sat in front of a fireplace and felt your face glow, that’s radiant heat. Windows with low SHGC reflect much of that heat, which is great in hot climates, or west facing windows on rooms that tend to overheat in the afternoon. It’s also great to stop the heat from your house radiating out. This is achieved by adding a coating that reflects this specific frequency of energy.

In your cold climate it makes sense to have:

• low U values everywhere (less conductive heat loss from your warm house to outside)

• low SHGC on north/west/east facing windows (heat from your warm house won’t radiate through your windows to the cold outside)

• high SHGC on the south facing windows. Here you’ll gain more radiant heat from the sun than you’ll lose, so it makes sense to maximize that free heat.

This is a useful article on how it works and might explain why you’re getting conflicting information.
https://www.buildinggreen.com/news-article/how-read-those-darn-window-performance-stickers

Funny - I didn't see any confusion.

Vancouver is not cold. Not using the US as a reference point. Not using Canada as a reference point. I live in NC and it isn't cold - but we are way colder than Vancouver.

What conflicting information is there for OP?

The GHG issue is not something most in the US are used to and, by looking around, it rarely seems to factor in decision making. That is far more confusing/conflicting than u values and SHGC.

The SHGC issue is relatively minor - mainly because it doesn't incur significant cost. Sure - high SHGC on south windows in climates with minor a/c seasons. That is theoretically cheap and I say theoretically because it is harder to find - especially when paired with low u values. The GHG mitigation in a relatively cloudy, relatively warm city from this is minor. But that would depend on how much southern glazing there is.

The OP might actually benefit from high SHGC on east windows at least and maybe west. Since a/c is from hydroelectric plants, there is low to no GHG issue. So while it will cost some electricity, it will save some gas. Financially maybe a wash but not in GHG.

That being said, I have no idea the relative cloud cover in the morning vs evening; winter vs summer. etc. Also no idea what tree cover the OP has. Vancouver is a climate unlike the vast majority of the US.

OP - how far along are you on construction?

Interesting how developers feel that the GHG rules effectively ban natural gas from new construction in Vancouver. I guess your example is a good one of why the rule doesn't but it sure makes NG a tough thing to incorporate. (and you can probably tell, I don't feel it is worth it).

Use gas for cooking and fireplace. Given your electric service issues, I would throw in tankless hot water. But anything else is not worth it. Any idea what renewably produced gas is going to cost in 10 years? I don't.