House Building - Glazing

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Wazza69

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#298968 31-Jul-2022 11:41

Hi All,

My Dad is building a 2 bed house for his retirement in Blenheim and is on a relatively tight budget. He is weighing up what sort of glazing he should get out of standard double glazing, one or the other of thermally broken or e-glass or go the full hog with thermally broken or e-glass. The trouble is we keep getting contradictory advice and its hard to practically assess what would be worth the investment. If he doesn't invest in the glazing then it would allow him to upgrade his kitchen from something basic to something nice which is quite compelling but also aware that he wants to be comfortable in his retirement.

Has anyone got any experience of the different options? I know our 2012 new build has cheapish double glazing and I can still feel the cold from a meter away at night, especially around the frames and we also get condensation so I am leaning towards thermally broken but then again his architect recommended e-glass if he had to choose one.

The other side of the equation is internal moisture. He is adamant that he wants a fire place (romantic visions) but is also getting electric central heating for convenience. Would he be better to go for standard windows but with tickle vents to manage the air flow?

Thanks

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#2948544 31-Jul-2022 12:03

Can't help you with the windows but I was certain I wanted a fireplace, until we got ducted central heating. I am not missing the stacking of firewood, cutting kindling, getting rid of ash and the space that the fireplace takes up. I love being able to press a button and 10 minutes later having a warm dry house, being able to put it on a timer and wake up to a warm house.

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tweake

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#2948565 31-Jul-2022 13:53

the first thing to keep in mind is that new insulation rules come out next year.

so your going to get thermally broken glazing anyway (or pvc etc). also the country is now broken up into smaller regions for insulation spec, so i suspect the specs will have changed quite a bit for Blenheim.

all of that is a good thing. building basically auckland spec houses in south island has always been a terrible idea. current double glazing is similar performance to old wooden single glazing, thats how much difference the frames make.

keep in mind you can always upgrade a kitchen later, thats easy. very expensive and difficult to upgrade insulation/windows later on.

also the size of the windows impacts insulation value a lot. keep them smaller, especially on the south side of the house, makes a huge difference. fixed pane is cheaper but keep at least one opening window in the bedrooms for fire escape. if you use a ventilation system there is no need to open windows, so why have opening windows you never use. do not use sliding windows or doors. they seal poorly, unless you go for the high end ones, stick to hinged doors/windows as they seal better for the price.

e-glass if you can afford it. i think thats more of an optional extra.

trickle vents in windows is just a bad idea.

for ventilation either just open windows, or a ventilation system which is not all that costly for a 2 brm house.

fireplaces i always recommend for areas that are that cold its life threatening if the power goes out. otherwise heat pump, he will not miss chopping wood. the better the house is insulated the smaller and cheaper the heat pump is. i recommend one for the bedroom, but also check out ducted systems. its one system instead of two, and ducts are cheap to do. (tho i do recommend a "hot roof" design so the ducted system is inside the house.)

mattwnz

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#2948572 31-Jul-2022 14:49

tweake:

all of that is a good thing. building basically auckland spec houses in south island has always been a terrible idea. current double glazing is similar performance to old wooden single glazing, thats how much difference the frames make.

I don't believe this is correct. The R value is about 0.19 for timber or PVC frames with single glazing vs between 0.26-0.33 for double glazing in regular aluminum windows depending on whether it is regular clear glass ICU or Low E and argon filled. Then good curtains can also add to the R value.

tweake:

so why have opening windows you never use. do not use sliding windows or doors. they seal poorly, unless you go for the high end ones, stick to hinged doors/windows as they seal better for the price.

e-glass if you can afford it. i think thats more of an optional extra.

Opening windows for each room are required in the building code for natural ventilation. There is a minimum size , as well as a minimum size of window for natural light. The council should pick this up when a building consent is issued.

tweake

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#2948585 31-Jul-2022 15:35

mattwnz:

I don't believe this is correct. The R value is about 0.19 for timber or PVC frames with single glazing vs between 0.26-0.33 for double glazing in regular aluminum windows depending on whether it is regular clear glass ICU or Low E and argon filled. Then good curtains can also add to the R value.

Opening windows for each room are required in the building code for natural ventilation. There is a minimum size , as well as a minimum size of window for natural light. The council should pick this up when a building consent is issued.

what your missing here is the R value for wooden frames vers non-thermally broken aluminium frames.

basically the issue is that current window standard is ONLY for the glass. so it does not include the losses the frame makes. when you add the frame insulation value into it, current double glazing is same/similar to old wooden windows. those old thick wooden frames are well insulating compared to aluminium. this is for the typically minimum spec windows most homes get today which are not coated.

so your 0.19 vers 0.33 is for the glass only, not the whole window. there is a Branz doc on it if you want to check it out.

yes there is minimum size for windows, especially for light. however for ventilation the minimum spec only applies if you do not have forced ventilation. ie if you have a ventilation system no opening windows required (not uncommon on passive houses). but i still recommend big enough opening windows for fire escape, which should be plenty big enough for sunlight requirement and any ventilation requirement.

the problem is people put huge windows in which drastically lowers the insulation value of the house. not uncommon to get full wall length windows in bedrooms which also limits furniture placement in small rooms.

reducing window size cuts cost, makes small rooms easier to use and increases insulation value.

mattwnz

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#2948592 31-Jul-2022 15:54

I was referring to the NZ Consumer site that lists R Values, which does appear to take into consideration the different frame types https://www.consumer.org.nz/articles/double-glazing#:~:text=The%20R%2Dvalue%20depends%20on,of%200.26%20to%20a%20window.

tweake

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#2948598 31-Jul-2022 16:05

not the doc i was to referring to but its close.

https://www.building.govt.nz/building-code-compliance/h-energy-efficiency/h1-energy-efficiency/building-code-requirements-for-house-insulation/r-values-for-common-construction-types/#jumpto-windows-and-skylights

keep in mind spec will change depending on frame to glass ratio. the old windows i referred to are quite small, a lot of frame compared to glass.

MikeAqua

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#2949054 1-Aug-2022 12:49

I live in Blenheim and I had houses here with thermally broken and non-thermally broken DG. I would definitely get the thermally-broken kind. The non-TB gets condensation on the interior side of the metal framing and is cold to the touch.

The other consideration is the alignment between the centre of thermal mass of the window and the centre of thermal mass of the wall. Often windows are hung so that the frame protrudes beyond the exterior cladding, meaning that the thermal break is close to the edge of the exterior cladding. In this situation the thermal break can be bypassed by thermal bridging between the exterior cladding and the interior part of the window frame.

If I was building house I'd ensure the windows were inset, so that the thermal break is in line with the timber framing, not outside of it.

Mike

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timmmay

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#2949246 1-Aug-2022 15:23

PVC double glazing works very well. It comes in white, or white. It works very well, doesn't get any condensation.

lxsw20

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#2949259 1-Aug-2022 15:48

Eh? PVC comes in loads of colours.

MikeAqua

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#2949316 1-Aug-2022 16:13

timmmay:

PVC double glazing works very well. It comes in white, or white. It works very well, doesn't get any condensation.

I just can't get my head around that. Every exterior PVC building product I've seen, deforms under UV. I know it's popular in the N Hemisphere, but I can't see PVC as anything other than cheap nasty plastic. I think I'd rather have timber.

Aluminium, I know from professional experience, is very durable.

Mike

Jase2985

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#2949318 1-Aug-2022 16:18

lxsw20:

Eh? PVC comes in loads of colours.

the colour is a laminate on the PVC for the most part

Jase2985

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#2949321 1-Aug-2022 16:20

MikeAqua:

I just can't get my head around that. Every exterior PVC building product I've seen, deforms under UV. I know it's popular in the N Hemisphere, but I can't see PVC as anything other than cheap nasty plastic. I think I'd rather have timber.

why would they make it and sell if here with lengthy warranties if it wasnt durable?

i doubt in some cases you could tell the difference between an ali and an upvc window

tweake

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#2949332 1-Aug-2022 16:26

MikeAqua:

timmmay:

PVC double glazing works very well. It comes in white, or white. It works very well, doesn't get any condensation.

I just can't get my head around that. Every exterior PVC building product I've seen, deforms under UV. I know it's popular in the N Hemisphere, but I can't see PVC as anything other than cheap nasty plastic. I think I'd rather have timber.

Aluminium, I know from professional experience, is very durable.

my understanding is early imported PVC suffered that problem. i suspect now they make a more uv resistant version for downunder.

we have plenty of pvc house products that sit out in the sun for decades with no issues. eg gutters and downpipes.

as an alterative there is fibreglass which is understand is stronger and can be easily painted.

timmmay

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#2949458 1-Aug-2022 18:12

I have PVC that's a decade old that looks as good as new. I wash it with soap at least annually. There's a mountain hut in NZ somewhere that has had it fitted for 20 years and apparently it's fine too.

Wazza69

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#2949462 1-Aug-2022 18:24

Hi all. Thanks for the responses. Dad decided to go with the thermal break and the e-glass. It was the upcoming regulation changes which convinced him (although he would be slightly before them). I’m sure it’s the right choice

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