There are 8 French Doors, 1 entry door and 16 assorted windows.
Ah that may go some way to explaining the quote. All those French doors are going to be expensive. I'd assume the structural requirements may boost the gap between solid and thermally broken aluminium more than a window would. Every door requires double safety glass which pushes the costs up. So you have about 80m2 of glazing?
A thermally break shouldn't add 50% to the bill. Some other available thermally broken profiles will be cheaper than the Pacific Thermal Suit you were quoted for.
You don't have to get the same profile for all of the joinery. You could get thermally broken for the windows and front door and solid for the french doors. Or use a different supplier for the french doors.
The house is concrete block, filled with concrete in the voids, on solid concrete foundations. Roof is butynl over steel with pink batts but not to current specs probably.Old ceiling pink batts may be only R1.5 with slumping. Are the concrete block walls uninsulated?
This PDFgives an idea of how thermally broken performs versus solid aluminium with plain and high quality low e glass. Plain glass lets in 1/3rd more solar heat gain than XCel/Planitherm XN although this can be a bad thing in summer if the glass cannot be shaded. Going from plain single glazing to plain double glazing can lead to greater overheating in summer while the lesser heat gain of low e glass makes for easier daytime cooling.
The performance of solid aluminium varies heavily depending on the quantity of exposed aluminium relative to glass so the R value of a small window is quite bad relative to a large window where the frame has less influence relative to the glass.
A U value of n means n number of watts is lost each hour per m2 per degree temperature differential. So a 3m2 window with a Uw value of 1.6 where it's 10c warmer inside than out means 48w is lost per hour. The R value is the inverse, so an R value of 2 is a U value of 0.5, an R value of 10 is a U value of 0.10 etc. A higher R value is better while a lower U value is better.
The "thermoplastic spacer" is inside the glazing unit between the glass panes. There are aluminium spacers but you don't want that in thermally broken aluminium as it forms a thermal bridge between inside and outside. Planitherm XN or "LightBridge" as they appear to be calling it now and be specified with either, but XCel always comes with the thermal spacer.
A recessed installation like they do in Europe should improve thermal break performance and condensation resistance, instructions for AllSeasons can be downloaded from here. Aluminium joinery in Australasia is normally installed around the exterior of the cladding. Other New Zealand thermally broken profiles can be installed recessed but I'm not aware of other brands providing instructions. APL Residential Thermal Heart should benefit the most from this as it's the narrowest thermally broken profile which while making it cheaper to make does make it more vulnerable to losing heat with the standard installation. The Omega thermally broken profile has been overtly designed to cope better with being installed on the exterior. Most New Zealand builders aren't going to be very good with non standard installs.
Assuming a well insulated house in a typical winter situation, I'd estimate solid aluminium with low e double glazing to be about 0.45c cooler for room temperatures than basic thermally broken with low e double glazing. PVC would be typically approximately 0,2c warmer than thermally broken aluminium however performance does vary between different products and there is some overlap (U1.3 best German TB alu, U1.4 weak PVC). European PVC has thicker frames and with solar insolation averaging as high as 1.8kW/m2/day in mid winter the effect of thicker frames mounts up. Slimline PVC frames are available but you lose out in other areas like longevity and presumably insulation. In mid winter where the windows have curtains in front of them for 14hr/day the quality of thermal drapes mitigates the differences between different windows. Real world with good low e double glazing could be under 0.1c advantage for PVC after reduced solar heat gain and thermal drapes are taken into account.
As much as PVC is marketed in New Zealand as a premium product, it's mostly used overseas because it's the cheapest option meaning its popularity would rapidly decline if it wasn't. Aluminium does need a thermal break to perform thermally but PVC needs metal to perform structurally (they are usually 20% steel by weight). Only fibreglass joinery doesn't need to be composited with another material to perform.
Trusted
ID Verified
