Window U Value?

Test6699

After looking at geothermal and an installation cost of 23000 for a 3000sq ft house I have decided that there may be better methods.
For instance as well as extra attic insulation there is the option of upgrading windows.
An upgraded window will have pvc on one side and timber on the other. This brings down the u value. Also the glass itself is upgraded. A cost of about 200 euro per window extra.

Are investing in windows a worthwhile efficiency benefit?
Secondly if windows are upgraded, is a heat recovery system essential. -whats the point in putting vents into windows that you have just paid a fortune for.

Any other advice on windows.?
If an oil boiler is a necessity is there any way of making it efficient. A condenser isnt a whole lot of good when the temperature is at a high temp (required for heating radiators). Has there been any advances in radiators to make them more efficient (excluding thermostats)

Thanks

Mellor

What u-value are you upgrading from and to.
For example, its defo worth it to go from 2.0 to 1.2
Probably worth it to go to from 1.2 to 1.0, but it closer etc, to go past 1.0 is possible but will cost far more pro-rata.

badolepuddytat

Window upgrading from a standard DG 16mm of 2.2 to a super duper 1.2 will save the average house about 15-25 kwh/m2/annum (20% glazing, 2 story even sided window area)

for 23k,

1. really good heating controls (time/temp in every room (2.5k)
2. Cavity wall insulation (0.3) (2k) or externally insulate to 0.11 (about 15k)
3. Attic 300mm fiberglass from 150mm (E800) and U value 0.13)
4. solar panels 4.5k
5. Stove in place of open fire 1.5 k
6. High efficiency boiler. 2.5k

unless you have no cavity and outside insulation is a must, then 10k with make a very EE house. Windows won't payout for 60-120 years.

Before spending that amount of cash, i suggest you get a BER done (in sept/oct for existing house). or at least consult a professional. local energy agencies (tied to local authorities) should be able to give some good free advice.

where are you located?


4.

sas

badolepuddytat wrote: »

or externally insulate to 0.11 (about 15k)

15k to externally insulate a 3000sq ft house? Care to pm me the name of the company that'll do it for that sort of money?

Test6699

This would be a new house in Limerick county so designed with the new regulations in mind.
The standard U value is 1.9.
For 3500 attic insulation is increased to 300mm and soft core glass is used. The U value of the windows goes to 1.6.
For an extra 5000 the window frames can be upgraded and the u value reduces to 1.3 I think.
This is all through one of the major window companies in Ireland.

I think upgrading the attic insullation is a no brainer but the 5000 option. Worth it?

Final question is Heat Recovery Ventilation. Is it worth the 5000 installation cost? I like the idea of no vents in the windows themselves-cuts noise and must help in insulation, but does it pay itself back?

Chimpster

Test6699 wrote: »

Final question is Heat Recovery Ventilation. Is it worth the 5000 installation cost? I like the idea of no vents in the windows themselves-cuts noise and must help in insulation, but does it pay itself back?

Unless your house achieves an air tightness result of less than 3 m³/h.m² on completion then the effeciency of your MHRV system will be alot lower than it could be and your payback will be alot longer. Pay good attention to air tightness, get the house tested.

Also select an MHRV unit that has been fully tested and registered on SAP appendix Q. Any of the ones on this list have been tested.

http://www.sap-appendixq.org.uk/searchresults.jsp?parentID=1&categoryID=3&bestPracticeCompliantID=&companyID=&productSearch=&performance1ID=&performance2ID=&performance3ID=&Submit=Search

PM me if you want any more details. For the record, I run an Independent Building Energy Management company here in Galway.