Doing all that without reducing infiltration gains/leaks will not improve the position as much as it can, but then you need an MVHR system.
onq
I hope you don't mind me asking a question here, as you do seem to know your stuff.
I too have recently been considering cavity wall insulation, but I have not yet spent a winter in the house (only moved in Feb this year) and was thinking about waiting until I see how I fare this winter so I can make a better decision next year.
Anyway, I have noticed that my back bedroom (downstairs) is the coldest room in the house. The rear of the house is generally north facing, although not directly. This bedroom sides on to the driveway and the rear of the house. It is also the childrens room, which worries me a bit for a possible cold winter. The opposite bedroom on the same wall but towards the front of the house (south) is a lot more cosy, despite also backing on to the driveway.
After reading this thread I was thinking that if the house feels generally ok over the winter maybe it would be better to do internal insulation on that cold bedroom only? Surely that would be a more cost effective option that cavity wall?
Perhaps you could give a rough idea of how much it would cost to internally insulate one bedroom with 2 external walls? I think the room is approx 12ft x 12ft.
Thanks.
I had a new bungalow with cavity insulation, in the winter I would still get condensation running down the end walls in the bedrooms. I would personally recommend insulating the inner wall not the cavity.
It never made sense to me having the cavity insulated, because there is a mass of blocks to heat up on the inside which takes time, and the blocks also transmit heat to the cold floor/foundations
I understand the principles of MVHR, however my concern is the bacteria build up within the filtration system. How will this pan out over the years as more and more systems get installed? How often should the filters be changed, 3 months, 6 months, 12 monthly intervals?
How will it be monitored and will, for example, tenants in a rented property with MVHR installed change the filters at the appropriate intervals?
I think it was last year on Duncan Stewart's programme where the lady with a lung disease was not told to change the filter and it was tested after 12 months and found to have millions and millions of excessive bacteria blowing through the home.
The problem with cavity fill is checking to see the entire cavity is treated.
Firstly I would like to congratulate you on your comprehensive reply.
In you opinion ONQ, would a thermal camera survey be able to determine if the cavity has been filled?
Also why do you not favour bead insulation?
I can't add to the technical discussion here, however, a few years ago, we lived in a 70s built bungalow which had poor insulation and a very low slope on the roof meaning it was physically difficult to insulate the attic. We got the cavity insulation done and it did make quite a difference.
A more serious concern is the transmission of cold smoke, fumes and gases around the house to the sleeping occupancy.
No fatalities have occurred thus far that I know of, but these issues are foreseeable.
Architects who are designing or certifying systems should consider them.
To answer your query I'd say one month, but each home will be different and only testing can answer this.
I am also very wary that a mass of such insulation spreading from wet external leaf to the wall ties, will conduct moisture to the inner leaf.
I also have wondered about this. If you believe the product literature, it suggests that any moisture will work its way down the cavity through the beads.
I'm booked in to have my own house done with cavity wall insulation next week. I've taken the day off to inspect the workmanship. Will let you know how it goes.
As regards checking to ensure that the cavity is adequately filled, is it not a matter of calculating the void to be filled and comparing it with the amount of material used.
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