Go to Forum Home Materials and products Replacement Windows – Do I go for A or A+ rated

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    • #31265
      Anonymous

        A quick query (hope I am in the right section for this).

        I am at the beginning of what will most likely turn into a lengthy refurbishment of a typical 1960's 4 bed detached house with rendered and painted traditional 11″ brick cavity walls under a pitched clay tiled roof – my goal is to significantly improve the performance of the house whilst not intending to head anywhere towards Passivhaus standards.

        Having looked at replacing the existing awful upvc double glazed windows with triple glazed alu-clad timber windows, (and having winced at the price of up to £30k), I am now looking at the more cost effective option of HED 0.8 Sheerframe upvc windows which from what I can see will be more cost-effective and better performing than the alu clad alternatives; after the windows are replaced, I plan to have the cavity within the external walls insulated with a pumped bead solution which I am hoping should improve the thermal efficiency of the house significantly.

        My question is that given a cost difference between A and A+ windows of around £4k, is it worthwhile investing this extra money, when the house will after all only have 11″ thick filled cavity walls when the project is complete? Will the windows 'outperform' the walls or could the money be better invested in other energy saving measures?

        As a post-script note it is interesting that the majority of companies I have approached have ridiculed the suggestion of triple glazing and it seems to be relatively unheard of in this neck of the woods (S Cheshire).

        Advice, suggestions and any feedback appreciated.

        Regards,

        HaydnT

      • #36982
        Anonymous

          Thanks Fostertom for guidance,

          The best pricing I could find was from Viking in Estonia; I did contact Russell Timbertech but for some reason couldn't obtain a price from them. The main problem I have found is having someone prepared to install who will also take responsibility for measuring up as everyone to date has shied away from this – I have knocked on many doors but they all remain closed which is also one of the reasons I have considered the Sheerframe upvc windows. It does seem a great shame that we have become a nation of upvc lovers – a bit like the old white vs brown bread and 'fizzy' beer vs real ale wars.

          On the other topic, do I take it that current thinking is that cavities should be left unfilled?

          Regards,

          HaydnT

        • #36983
          Tom Foster
          Participant

            Where are you? You could get a eco-minded architect, surveyor (sic), builder etc to take responsibility for size, ordering and spec – ask here and on Green Building Forum. On that basis, try Russell again.

            Cavities – that's my personal view – others may not agree … ?

          • #36984
            Nick Grant
            Participant

              As Tom says, unfilled cavities is his idea and probably not shared by most people. If you can't or won't insulate externally then I assume that even Tom would advocate insulating the cavity.

              If external insulation is an option then that needs to tie in with the window position in the wall and type.

              I can only comment on glazig spec' for very low energy homes in which case I'd go for very high insulation (without bothering to calculate payback) for thermal comfort and avoidance of condensation. Less of an issue if you are having to pump in heat anyway to stay warm with rads under the windows.

              Nick

            • #36985
              Anonymous

                I am using Al clad timber windows from AM Profiles in my build. This is a UK company that manufactures PassivHaus certified Hermann Gutmann windows under licence. I found their quote to be about half that of Internorm. I hope that helps.

              • #36986
                Anonymous

                  Thanks very much for replies, and to update, I have contacted a local practising AECB member who has come up with good suggestions and I have also contacted AM profiles and sent information for them to quote on: I will also try Russell Timbertech next week to ask them to quote too.

                  All in all therefore I am encouraged by the advice provided and hopeful that we will make good progress soon – and fingers crossed for a solution that does not involve upvc.

                  With reference to the insulation query, external/internal insulation of the walls is not really practical and so I plan to fill the cavities after window replacement with the insulation that will give the highest 'U' values (most likely expanded bead?)

                  Regards,

                  HaydnT

                • #36987
                  Anonymous

                    Thanks to all thus far and to update, I have abandoned alu clad windows on the basis of cost and needs; following a visit to Ecobuild I have obtained pricing from Howarth and am waiting for a quote from Russell Timbertec although at 3 weeks and counting it as taking longer than I had hoped.

                    With reference to the physical dimensions of the windows, the majority of companies seem to go for the 4-12-4-12-4 arrangement but I note the comment on 4-18-4-18-4 above – are there any companies who are producing this as a standard/as an option?

                    I will further update once pricing is back for a review of the cost/m2 prices.

                    Regds,

                    HaydnT

                  • #36988
                    Andy Mitchell
                    Participant

                      Yes 4-16-4-16-4 and 4-18-4-18-4 are available.

                    • #36989

                      Hope this is not off topic but replacement of windows sounds like one of the last things to do, not the first, if you have a finite budget.

                      An analysis last autumn of some (60s) houses in London showed that cavity wall insulation with airtight material (not beads, try PU foam as used now throughout the Netherlands), roof insulation (similar), sophisticated improvements to the heating, a superinsulated DHW tank and pipes, all cost in the range £0-50/tonne to save CO2. Replacement windows gave a cost of £1,000s/tonne.

                      The only low-cost measure that emerged on the existing 10-15 yr old PVC windows (frames and sashes were airtight in a pressure test) was to replace the existing SUs by really good argon-filled low-e warm edge ones. Given that the existing SUs were starting to fail, this gave a cost of saving CO2 of around £50/tonne.

                      I think leaving a cavity empty for 5 years merely guarantees 5 years of discomfort and filling it with beads giuarantees regret for ever more that an airtight material wasn't used.

                      HTH

                      David

                    • #36990
                      Anonymous

                        no suprises there about the sophisiticated controls on heating..

                        Even in the UK upgrading a condensing boiler by installing load compensation controls will save you around 25% of gas.

                        They are extremely cost effective, adding little or nothing to the cost of the installation, but do require to be correctly set up. Even so most have a user override function…

                      • #36991
                        Anonymous

                          Hi David,

                          Apologies for slight absence; still trawling through windows suppliers in between installing wood block flooring, decorating and the day job.

                          I am interested in your comment on –

                          “cavity wall insulation with airtight material (not beads, try PU foam as used now throughout the Netherlands)”

                          Do you have any contacts in UK for this type of insultation? Are suppliers moving towards this as a material?

                          Advice appreciated.

                          Regards,

                          Haydn

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