Target U-values… Cost/benefit sense check… What am I missing? 🤷🏻‍♂️

[Oz07]

With windows and doors is there a ballpark figure per m2 with mid range 2g vs. mid range 3g? @craig

 

Do you run into a similar issue with glazing and payback periods some of these top spec windows costing a lot. Especially as they wouldn't last as long as a wall. 

 

If having a house with average wall u value 1.8 there must be a certain u value window you can go for before it becomes uneconomical. Excluding the benefits of reduced noise etc etc. Average 4 bed with 30m2 glazing I bet ai could work it out. 

[JohnMo]

4 minutes ago, Oz07 said:

house with average wall u value 1.8 there must be a certain u value window you can go for before it becomes uneconomical

Would suspect it's down to the wall to window ratio and that will vary by room and by house.

 

Example

Our living room has nearly 30m2 of glazing and about 10m2 of external wall in total.  So going for high performance 3G wins the day, every day. For clarity our living room has more heat loss than the rest of the house in total. So we upgraded to to 3G.

 

I's all a balancing act something's make sense in one build and no sense in another. Generalising is choice decision.

 

 

[Crofter]

2 hours ago, Oz07 said:

If having a house with average wall u value 1.8 there must be a certain u value window you can go for before it becomes uneconomical. Excluding the benefits of reduced noise etc etc. Average 4 bed with 30m2 glazing I bet ai could work it out. 

1.8 is horrendous for a wall (you don't mean 0.18 do you?) but improving your existing walls is much harder than retrofitting better windows.

None of this is rocket science. It comes down to surface area and u value.