Double vs. Triple glazing. Is triple worth the extra?

spida

We have renovated an old house with internal insulation and lots of other bits. We left the windows to do another year because they were double-glazed already albeit old. Then the condensation came and the cold

Now we HAVE to replace the windows. We know the ones we want and just have to decide between double, triple and quadruple! Last one is definitely out!

U-Value :
Double Glazed :1.2Wm2K
Triple Glazed: 0.76Wm2K

As we have to get the sills done at the same time (they're about to fall off) the job will be expensive anyway. So the extra for triple adds about 10% to the price. Something we can afford but not if it's not worth it. Also I have a concern about diminished light through the triple-glazed panel.

What I want: well I want to be able to have my house warm without having the boiler going 24x7. I'm prepared to pay up-front even if it would take many years to earn the money back, just so I don't have to be worried about how much sitting in a warm room is costing me minute-by-minute.

jj build

JUST a quick reply. i have went with double glazed with k glass in older houses and made sure the the reveals and lintel where well insulated with expanding foam and entire reveal covered in insulation slab and also make sure sill and window board are well sealed with silicone all around . I always have great results .

TopTec

Like you, I am doing an old cottage refurb. Getting towards the end now. In the main buildings I put standard double units and in a large new sunroom I had triple, mainly due to the large surface area of glass in there.

The quality is a world apart and the sun room is quicker to heat up, retains more heat, and is quieter that the rest of the cottage. The units are a lot heavier than the doubles and take more time to fit. I don't notice any difference in the light coming in but I have a large glazed area so any reduction would be reduced.

My only problem is that it gets too hot in there in the summer and permanently have the vents and transom windows open.

I would definitely fit triples in the rest of the cottage if I could afford it.

TT

Calahonda52

Op, if u are getting sills done then build on the ideas that jj alludes to in his reply and try and reduce the thermal bridging that wil occur if u just do a straight replacement. EF is NOT airtight so you need to tape the window frame on inside with airtight tape, not just any old tape.
The math on the DG vs TG is easy enough.
Take the difference in the two U Values, get the window areas, take a stab at the heat requirements by reference to a concept called heating degree days and if u are heating with gas use 5 cent a kWh.
Heating degree days is a method of estimating the heating required based on outside temps and inside temperatures.
The figure will be an annual cost of the extra heat loss with DG over TG.
Am on a tablet here so will try get back later with example.

The one thing to remember is that if the room is only used occasionally then the heating required is less and therefore the savings.
Eg if its 14 degrees inside and out, no savings with TG vs DG

BryanF

spida wrote: »

We have renovated an old house with internal insulation and lots of other bits. We left the windows to do another year because they were double-glazed already albeit old. Then the condensation came and the cold

Now we HAVE to replace the windows. We know the ones we want and just have to decide between double, triple and quadruple! Last one is definitely out!

U-Value :
Double Glazed :1.2Wm2K
Triple Glazed: 0.76Wm2K

As we have to get the sills done at the same time (they're about to fall off) the job will be expensive anyway. So the extra for triple adds about 10% to the price. Something we can afford but not if it's not worth it. Also I have a concern about diminished light through the triple-glazed panel.

1.2wm2k = approx 20mm EPS (polystyrene) insulation
.76wm2k = approx 40mm EPS

do not be concerned by the light reduction, discuss this with the windows company's, IMO you will not notice any reduction

you mention condensation: you will need trickle vents in the windows or wall vents. you need to overlap any new window with insulation to try and limit thermal bridges (cold bridges) which will allow internal water vapour to condense. good quality/ u-value windows often move the condensation problems to the reveals or to the next weakest insulated surface