Most important home upgrade, Home ventilation vs double glazing

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k262626

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#222887 2-Sep-2017 08:43

Hey All We have just purchased a 1965 stucco house in the Nelson Tasman region and are looking for advice, the house has insulation in the roof and under the floor as well as a newly install free standing fire what would you recommend as the next step? options I have thought of replace all the windows with double glazing or install a home ventilation system eg HRV, or do both?

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#1857090 2-Sep-2017 08:48

What problems does the house have? Is it cold? Is it wet? Do you have very wet windows in the morning? No point throwing money at something that doesn't need it.

Having said that, I found that double glazing helped keep the heat in well, but adding ceiling insulation tends to have a better return on investment. I had loose fill wool insulation, I added pink bats with two layers in some places, making almost a foot of insulation, adding the extra insulation made a big difference. Wall and under floor insulation made a small difference. Putting a ground sheet under the house made a big difference to dampness and smell.

A ventilation system does help drive out damp air, making the house easier to heat. You're better off with heat recovery ventilation - not the brand, the technology. Cleanaire does it well. I run my basic non-HRV system on a timer, because all it does is pump in cold air. In winter it runs a little in the morning and all afternoon, plus a little bit in the evening. In summer it runs morning and evening. I don't use air from the ceiling cavity, it's hot and smells, I use fresh air from the eaves.

tchart

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#1857099 2-Sep-2017 09:06

Double glazing would be my choice

Fred99

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#1857108 2-Sep-2017 09:13

Retrofit double-glazing is probably a waste of money unless the window joinery needs to be replaced anyway for other reasons. (or you want double glazing for other reasons - sound-proofing etc).

Payback time for any energy saving is many decades.

Payback times for the more permanent secondary-glazing systems were discouraging and much the same whatever the system. Dunedin had the best payback at 13-15 years, followed by Christchurch (15-17) and Wellington (16-18). Auckland was in the region of 28-30 years.

Payback times for new double-glazing are likely to be similar or even higher.

timmmay

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#1857116 2-Sep-2017 09:34

It all increases comfort though. This year we have double glazing, and we don't turn the heating off, because we have a young child. Even though the temperature gauge says the same thing, the house feels much warmer.

Double glazing actually increased the noise we get through, even though the very old windows didn't seal properly. Previously we had thick wooden frames, glass, with cheap retrofit "double glazing" that was a 3mm thick rigid plastic sheet inside the windows. When we moved to PVC and proper double glazing we got a lot more noise in. The wooden frames blocked it well. The PVC frames are really just two thin pieces of plastic, and there's a gap between the bottom of the frame and where the glass starts. The glass sits on some little plastic feet. If that was filled in with something it might absorb more noise.

Bung

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#1857129 2-Sep-2017 10:24

Fred99:
Retrofit double-glazing is probably a waste of money unless the window joinery needs to be replaced anyway for other reasons. (or you want double glazing for other reasons - sound-proofing etc)

I was asking a builder about double glazing in relation to a door we want and his argument was if we would pull a curtain across the door at night double glazing wasn't that necessary and it would reduce solar gain during the day. We aren't likely to ever need cooling.

Fred99

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#1857135 2-Sep-2017 10:50

Bung:
Fred99:

Retrofit double-glazing is probably a waste of money unless the window joinery needs to be replaced anyway for other reasons. (or you want double glazing for other reasons - sound-proofing etc)

I was asking a builder about double glazing in relation to a door we want and his argument was if we would pull a curtain across the door at night double glazing wasn't that necessary and it would reduce solar gain during the day. We aren't likely to ever need cooling.

I basically had to put double glazing into a new set of cedar french doors which I put in to replace a window. Window area in the doors is larger than window area of the original, I'd have had to prove that I'd upgraded thermal efficiency elsewhere (which I had done anyway). Much easier just to do what you're told rather than argue with council.

Yes - curtains can be just as or more effective than double glazing. Need to be floor to ceiling (or pelmet - if fitted) - or they can actually make things worse - increasing air flow down the gap between the curtain and the window, like a chimney in reverse. They also help reduce noise. Of course double glazing and curtains increases benefit over either alone.

R rating on double glazing is something like 0.5.

I'm guessing that one of the reasons some people seem convinced double glazing is better than it actually is, is that they're comparing old drafty single glazed to new well sealed double glazed.

Hammerer

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#1857151 2-Sep-2017 11:54

It is best to insulate where you get the most financial benefit which is why ceilings are insulated first. Windows comes next in terms of heat losses in an older uninsulated house:

Ceiling 30-35%
Windows 21-31%
Wall 18-25%
Floor 12-14%

As you've got insulated ceilings and floors then the heat losses will be something like this with windows now closer to half the heat losses.

Here's some relevant R values:

Exterior wall uninsulated typically R 2.0
Exterior window single-glazed R 0.15-0.19
Exterior window double-glazed aluminium R 0.25-0.32 (i.e. without thermal break to prevent heat flow through the frame)
Exterior window double-glazed high performance R 0.34-0.51 (typically PVC or wood)

It's difficult to recommend double-glazing financially unless I am building new or I have a specific problem I wanted to resolve. Other options are financially attractive when compared with double-glazing:

Opaque curtains can add up to R 0.25-0.50. In my house we have some pelmets and double/triple-lined our curtains so, when they are closed, we got a much greater insulation benefit than double-glazing.
Net curtains (sun filters) can add up to R 0.20-0.40 as they reduce convective heat losses through the windows and can be used during the day as well as behind opaque curtains. The Consumer articles on this are very useful as are beaconpathway.co.nz. They found that if filters are installed close enough (e.g. 1-2 cm) to the window then they can perform better than much double-glazing.
Insulating film taped to the frames (doesn't work well for aluminium) can add R 0.30-0.40. They're not permanent but they are much less than $50 a typical window and they can last for several years. I use the film on the colder bedroom windows on the more south-facing walls of the house. I also use it on windows high up on the walls where I don't need to look out. Double-glazing would be much more aesthetically pleasing in living areas.
Bubble-wrap traps the air in small cells so can over R 1.0. Ugly as but fine in rooms that are never used or you don't need to look out the windows.

It's a bit sad that none of the window options can get the windows to the same level as typical uninsulated walls.

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timmmay

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#1857163 2-Sep-2017 12:38

Hammerer:

It's a bit sad that none of the window options can get the windows to the same level as typical uninsulated walls.

You probably can, if you want to spend the money. Triple glazed can get to above 1.0, according to one page I read, but to get up to 2.0 would probably be too expensive to bother.

cadman

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#1857168 2-Sep-2017 13:25

Double glazing. Ventilation is easily achieved by opening the windows.

Aredwood

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#1857239 2-Sep-2017 16:50

If any bedrooms have windows above the beds. Definitely get those windows double glazed. As it will reduce cold air dropping onto the beds.

A 1960s house especially with a fireplace will already have a lot of ventilation due to air leakage. So not much point in getting a ventilation system. And keeping the house warm 24/7 will increase heat losses due to air leaks as well. So best to fix heating and insulation problems first before worrying about ventilation.

And if the house is damp due to it being in an area surrounded by trees, or another reason causing the outside to always be damp. Then no ventilation system will fix damp issues. You will need to use dehumidifiers instead.

Fred99

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#1857242 2-Sep-2017 16:59

Hammerer:
It is best to insulate where you get the most financial benefit which is why ceilings are insulated first. Windows comes next in terms of heat losses in an older uninsulated house:

Ceiling 30-35%
Windows 21-31%
Wall 18-25%
Floor 12-14%

What's missing there is cost.
You can often DIY install or upgrade ceiling and floor insulation for a few thousand dollars.
Double glazing full replacement cost probably more like $25k. Walls - unless part of a re-cladding or internal re-lining is probably similar high cost.
For a 60s house, first thing I'd look at is the state of window and door joinery. Even if the windows are sealing OK, then wooden architraves are the seal between the wall cavity and the interior of the house. They warp and/or come loose, and let a lot of cold air in. Almost completely pointless IMO if insulation is put in, but the house is draughty.

Our 210 m2 approx 1962 house in chch, single glazed, but fully insulated walls, floors, ceilings, is heated throughout with 2 x heat pumps, total capacity about 8kw, on 24/7 in winter maintaining 21 deg and 18 at night (I don't like 21 deg overnight - it's uncomfortable. )
It was heated solely by log burner last winter. Have not used the log burner over this winter. Increased power cost has been $100/month. If we could halve our heating cost with double glazing (very unlikely) then payback period would be over 50 years.

timmmay

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#1857246 2-Sep-2017 17:30

For seven reasonably large (2x3.5 on average) PVC windows plus one small 0.5 x 1m PVC window it cost me around $13K installed. This was retrofit, using the existing frames. It then cost $3K for painting, including stripping frames to the wood on the outside, but we painted the inside frames ourselves.

I guess double glazing might reduce the heating bill by 5%, maybe 10%. We did it because the old windows were stuffed and needed to be replaced, being warmer was a nice side benefit.

Fred99

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#1857304 2-Sep-2017 18:53

I got quotes to remove/replace our window joinery, all were around $25k, but it's quite a large house with large windows for its age. I was only looking because I had to do quake repairs, and there was a lot of work involved in bringing existing flashing system up to present building code while I did a full re-clad. Whacking in new joinery would have been easier, but I liked the old cedar and rimu joinery, all in good nick, varnished. Most of the smaller windows double hung sash with friction/spring mechanisms. I was able to disassemble and service all of these while I was working on them. Was an architect's own home. He was clearly quite particular. It seemed to be the right thing to do - preserving a bit of history.

GGJohnstone

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#1857503 3-Sep-2017 10:16

The mathematics of R factor is disingenuous but bought into perspective if the total heat loss from my house is apportioned to window and other. Then the argument is more in favour. Compare the noise from an open window with a closed window and then a closed single glazed to a double glazed for a positive spin.

Doubling the ceiling insulation was a more cost effective buts D I Y. H R V was pointless in my house at this latitude. In a relatives house it was possible to use that system to keep the closed up unused rooms fresh and have the whole house more secure when it was unoccupied.

About 20 year ago estimates were gained that required over $55,000 for my 1970 house to be double glazed. All windows and frames replaced non thermal break and probably white custom wood to make the house feel like a dentists waiting room or hospital.

More recently retro fit quotes came in for half that figure but were still extortionate and so easy for the manufacturer and if they were asked to manage the whole job with the cost plus-ing of builders and delivery to complete the work their prices would have equated to free winter electricity for ever if the money were banked at 2% interest instead. Common tradesman normal charge out rates include tax toll calls consumables and Xmas Cake anywhere in this sparsely populated province.

The job has been done now by a happy crew of five workers in one day. 42 lights including a ranch slider and a wooden door window. Measurable improvements, noise, heat retention, drafts from behind drapes, coal and electricity consumption. Optically better glass compared with the 50 year old replaced.

Compared with large market European standards New Zealand is a long way behind in building insulation. More regulations needed. I have seen almost brand new houses built with single glazed attached garage windows. A few dollars less initially but a massive cost to update because it was not illegal.

tukapa1

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#1857568 3-Sep-2017 12:40

cadman:

Double glazing. Ventilation is easily achieved by opening the windows.

This.

After having done a complete reno of an older home this has made a big difference.

I don't know why it is so hard to open some windows (and I live near a snow capped mountain).

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