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Double Glazing and Cavity Wall Insulation

Moved house a few months ago into a detached late 1980s build.

The cavity walls aren't insulated and the UPVC windows are all past their best. The windows at the moment do not have trickle vents and there are no extractors in the bathroom or en-suite but the house doesn't suffer from damp or condensation. However the house leaks heat very badly - not ideal from an environmental perspective.

We are planning on getting the walls insulated (and attic insulation improved) and we have the windows and doors booked in to be replaced.

The glazer came round to measure up yesterday and he says he wouldn't recommend trickle vents as they take the energy efficiency from A to G (his words). Wasn't expecting this response seeing as trickle vents are part of new-build building regs.

I was thinking that new glazing, improved insulation and trickle vents in the bathrooms at least would be the way to go. Anyone got any first hand experience with this sort of thing?

We're essentially aiming to have the house 'greener', ie cheaper to heat, but don't want to end up creating a new issue (damp) by solving another.

Posts

  • rjsterryrjsterry Posts: 19,292
    We're going to need a building maintenance thread at this rate 🙂. Yes, there is a bit of a conflict between the need to provide adequate ventilation and the need to reduce heat loss. Older buildings tend to have lots of gaps around doors, and windows, which unwittingly provided additional background ventilation. This can render insulation in walls redundant if cold air is just bypassing it and flowing directly into heated spaces. What you are aiming for is controlled ventilation rather than draughts.

    As you make the building more airtight, without good extraction you will tend to increase the build-up of moisture in the air. This will then condense on any less well insulated parts of the structure - also known as cold-bridges - so it is important that whoever does your insulation takes care with awkward corners and junctions. Edges of lofts are a common problem area as it is difficult to get the insulation right into the corner to meet up with the wall insulation.

    So, if you are looking to improve the overall energy efficiency of the house, I think for bathrooms, utility rooms and kitchens you need to be looking at the best extractor fans you can afford to get rid of humid air after showers/cooking. You can also get ones which run continuously on a low rate and then boost up to full power when operated by light switch or humidistat. Trickle vents are only really good enough for rooms where not much moisture is generated, but maybe shop around as not all window systems are equal in that regard.

    If you really want to go for low energy use, you can install a whole house MVHR (Mechanical Ventilation with Heat Recovery) system. This consists of a big box, typically in the loft, with ducts running to each room and to outside. Fresh air is pulled in, and passed through a heat exchanger before being distributed to bedrooms and living spaces. At the same time, stale air is extracted from bathrooms and kitchens and waste heat transferred to the incoming air via the heat exchanger. These do come at a cost, and require a bit of space, but they do mean you can seal doors and windows nice and tight without worrying about condensation and mould growth.

    Hope that's useful.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

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  • joeyhalloranjoeyhalloran Posts: 592
    nibnob21 said:

    he says he wouldn't recommend trickle vents as they take the energy efficiency from A to G (his words).

    I am guessing his statement was hyperbole but our 5-year-old built house with trickle vents has an energy rating of B.

  • surrey_commutersurrey_commuter Posts: 13,007

    nibnob21 said:

    he says he wouldn't recommend trickle vents as they take the energy efficiency from A to G (his words).

    I am guessing his statement was hyperbole but our 5-year-old built house with trickle vents has an energy rating of B.

    must be an inverse relationship as my house has no trickle vents and is rated E
  • rjsterryrjsterry Posts: 19,292
    I think we're confusing the rating of the whole house and the windows themselves. Having seen how little work goes into assessments of existing houses, those ratings are very approximate anyway. The windows will have been more thoroughly assessed.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
  • nibnob21nibnob21 Posts: 115
    Yes, he will have been referring to the rating of the window itself.

    I thought with trickle vents that you can open and close them anyway, so I'm not sure why they wouldn't be fitted as standard these days even if the windows they're replacing don't have them. Or am I missing something? Surely the big drop in energy performance would be based on having them all open all of the time.
  • rjsterryrjsterry Posts: 19,292
    edited 7 April
    nibnob21 said:

    Yes, he will have been referring to the rating of the window itself.

    I thought with trickle vents that you can open and close them anyway, so I'm not sure why they wouldn't be fitted as standard these days even if the windows they're replacing don't have them. Or am I missing something? Surely the big drop in energy performance would be based on having them all open all of the time.

    The performance will be based on a 'standard' window, which won't have trickle vents. They're not much more than a slot cut through the frame with a little flap to open and close on one side, and a grille on the outside. The window frame profile will be designed to isolate the inside and outside faces from each other to minimise heat loss, and cutting a slot through it negates a lot of that.

    They are sort of standard these days, but you can avoid them if you have other means of removing stale air and allowing fresh air in.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
  • nibnob21nibnob21 Posts: 115
    Yeah and I guess therein lies the problem, in that at the moment we don't have any extractors in the bathrooms. But they are both rooms that will be getting gutted and refitted, so proper extractors will be on the list at that point.

    Once the windows are replaced and cavity insulation installed, for the interim period before the bathrooms are redone and extractors are installed I guess it'll be the traditional method of simply cracking the window open a bit after a shower!
  • elbowlohelbowloh Posts: 4,748
    We definitely need to improve ventilation in our place. Just seems too bloody cold.
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  • step83step83 Posts: 4,027

    nibnob21 said:

    he says he wouldn't recommend trickle vents as they take the energy efficiency from A to G (his words).

    I am guessing his statement was hyperbole but our 5-year-old built house with trickle vents has an energy rating of B.

    Would agree, had new windows an doors last year, all the opening windows have a trickle vent on them.
    Infact, this is what we have

    https://www.formulaonerange.co.uk/product/casement/

    Thats using standard 28mm double glazed with Argon gas between the panes. Previous owner had cavity insulation done just left the old wooden casements in so it was never warm, new windows an much better.
    I have had the vents open most of winder an not had any problems, bar when the wind is blowing at the window it can get a little noisy so you just snap them shut.

    Other option would be the latch on the window, no idea its proper name but you can open the window a touch an lock it in place, allows way more ventilation than a trickle vent good option with things that like going out windows like children as you can lock them. Likely colder though especially in winter.
  • nibnob21nibnob21 Posts: 115
    Yeah difficult to know what to do. We live in an area of the midlands where it isn't particularly wet (not like where I grew up in the south west), the house is detached but not particularly exposed to harsh weather, driving rain etc.

    So really, any damp would be a result of internal condensation from breathing, cooking, bathing...

    We have an extractor hood over the hobs and we both practice good bathroom discipline with wiping the shower down afterwards with a squeegee, so perhaps I'm worrying about nothing.
  • rjsterryrjsterry Posts: 19,292
    nibnob21 said:

    Yeah difficult to know what to do. We live in an area of the midlands where it isn't particularly wet (not like where I grew up in the south west), the house is detached but not particularly exposed to harsh weather, driving rain etc.

    So really, any damp would be a result of internal condensation from breathing, cooking, bathing...

    We have an extractor hood over the hobs and we both practice good bathroom discipline with wiping the shower down afterwards with a squeegee, so perhaps I'm worrying about nothing.

    You're not worrying about nothing, but I think until you refit the bathroom you should be alright with being a bit more conscientious with opening windows to let in fresh air. I guess from the age of the house you won't have any open chimneys, but these can also help with ventilation.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
  • rjsterryrjsterry Posts: 19,292
    Also try not to have large bits of furniture pushed up against external walls as that is a typical place to get a bit of mildew if the room is a bit under ventilated.
    1985 Mercian King of Mercia - work in progress (Hah! Who am I kidding?)
    Pinnacle Monzonite

    Liberal metropolitan, remoaner, traitor, "sympathiser", etc.
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