Given the upwards march in energy prices and the need to insulate, insulate, insulate before considering a heat pump....
I currently have 270 mm of Kanuf eco roll loft insulation laid as two layers, 100 mm between the trusses and 170 mm on top perpendicular to the first layer.
I'm wondering whether its a worthwhile exercise to fit Rigid PIR sheet insulation under the tiles between the trusses?
I can get them cheaper as seconds and I would retain the existing Kanuf loft insulation.
(I already know baout the need for ventilation so would screw on 50 mm battens to teh sides of the trusses before fittign said PIR slabs.)
I currently have double glazing with Low E coatings and Argon filled sealed units. Is it worthwhile replacing with ttriple glazing? is this just the sealed glazing units or the whole window?
Is this a warm roof or a cold roof? In other words are you planning to seal the roof so the ventilation is *only* to the rafters and tiles behind the PIR, or are you going to retain ventilation to the loft space?
If it's a cold roof, PIR against the rafters isn't going to help since air can move into the roofspace past it. If it's a warm roof, you would need to seal at the soffits and think about what happens to condensation (since the air in the roof is warmer, it'll contain more moisture - if it contacts anything cold it'll condense).
Once you get above a certain level of insulation you end up with diminishing returns:
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and 270mm is already at the top end.
If it were me I'd see if I can get hold of a thermal camera (there might be a local 'green' organisation who will let you borrow one, or you can hire) and look for cold spots. Those give a much better return because you can address what actually matters - you might find a draught you didn't think of.
Again, look at the U-values. You might find that's diminishing returns as well. The frame system contributes to the U-value - if you had an old thermal-bridging aluminium frame no amount of triple glazing is going to help.
The main part people miss is the floor. It's not always straightforward to do something about, though.
You may find it useful to do a heat loss calculation. Put in the dimensions of your rooms into a heat loss calculator and tell it what they're all made of. It'll give losses for each surface - attack those with the biggest losses. It doesn't really account from draughts, which is why the camera helps too.
Changing existing double glazed windows for triple is not likely to be economic purely on energy saving grounds.
I replaced 2 6'x6' 20 yr old double glazed upvc patio doors with triple glazed ones recently at a cost of circa £3k (more for amenity than anything else) and have not noticed any improvement in warmth/heating bills or noise.
+1 (A couple of years ago I did the calculations for replacing the existing DG windows in my living room with triple glazed units and they seemed to show that I would save about £15 a year.)
Whilst I agree that the calculation route is no doubt the most accurate, it occurs to me that it might also be instructive to simply look at the energy used.
I guess I could get my actual heating use by subtracting the summer month level of gas consumption, when I would just be using the hob and water heating.
What figures would be good for a 1970s reasonably well-insulated
your house doesn't have an EPC, look at the EPC of your neighbours on epcregister.com to get an idea)
This gives some numbers for properties of different types in Scotland:
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roughly matches yours.
In the last place I had with gas (so you get the consumption on the bill) it was about 15000kWh (1940s mid terrace, rated borderline D/E). Obviously usage doesn't take into account hot water and cooking (gas cooker, electric showers in that case).
I'd also add, what about all the houses which do not have cavity walls, like most of them around here. I do not notice much of a problem with the walls being cold, I have to say, but one thing I have noticed since having better fitting doors of the double glazed kind is condensation on the ally window frames which are now quite old, but I'm really not going to re glaze the property this side of next summer, its not pleasant when you have bish bashers, big gaping holes and dust and foam all over the place. grin Brian
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