Brick cavity wall insulation - experience?

[Toodeloo]

I’m after your recommendations re cavity wall insulation, please. In a 60s mid terrace. On a hill but not majorly exposed. I am replacing all windows and doors soon and the loft is insulated as well but the house is brick built and quite cold at times. I’m worried about possible damp issues... anyone had it done? What did you think?

Exposed coastal location here. Walls and pointing in good condition, no spilling gutters or leaking downpipes. No cracked render or damp parapets. No gaps round windowframes. No mortar snots in cavity. Cut heating bills dramatically and no damp or other problems.

If you have defective walls, they must be rectified first.

If the installer puts insulation into defective walls that have not been rectified, and damp ensues, he can be forced to suck out the insulation at his own expense. So you will probably find that they examine your walls carefully and refuse to proceed if they have any doubts.

Oooh. That’s very good to know, thank you! As a single mum I am entitled to a few grants and the cavity wall insulation is one of those I’ve looked at. I need to have a closer look at the walls but it’s rendered almost throughout and looks decent (year old survey didn’t list it as needing done soon either). Gutters fixed recently and no problem with down pipes. Windows and doors will be done and checked over by Windows advice Architect (and come with 10 year warranty) so I don’t see that becoming a problem. Only question: would the presence of airbricks make a difference? Used to be hot air heating many moons ago... and, to go for front & back or just the side that gets most of the wind?
It’s actually sad how excited I get about home improvements...!

CWI is actually not very expensive. I can't see a reason to penny-pinch on the walls.

By the time two or three workers have rolled up in their van, unpacked the equipment and hoisted themselves into the air, one wall more or less won't make much difference to their working day.

If you house still has airbricks that allow cold air into the cavity, they will be sealed.

Airbricks that ventilate under the floor will be left open. You can tell which they are by poking a knitting needle or unfolded coathanger in.

btw when the windows and doorframes are taken out, you can look into the cavities. See if you can see lumps or mortar hanging off the ties, or piled up at the bottom of the wall. It's possible to rake them out and use a powerful vac on a big pipe, but not easy. There may be specialist contractors. The builders never thought that anybody would ever look inside the walls so were often careless.

All very good points and exactly what I needed. Thank you! I love knowing what’s going on with my house so I’ll have a good nosey about whilst they’ll be doing the windows anyway.

Do you have a coal fire/wood burning stove/ gas fire? When i had my CWI done they insisted in drilling a hole in my wall for ventilation because we had a coal fire. Managed to pursuade them to put it in the east facing wall rather than the north facing wall they were going to put it in but in my opinion it negated any benefits of the insulation - they only put a grill over the hole!

There is an old fireplace but it’s all boarded up so hopefully no bother there either. Fingers crossed! The only thing that held me back so far is the worry about it causing damp.

@bigbluebus

A very superior method is to run a duct under the floor, with a (usually brass) grill just in front of the fireplace so that the air required for the chimney to draw does not have to pass through the room and cause draughts. This is sometimes seen in rather grand old houses with big open fireplaces. It's not often done but worth a thought. I imagine the regulatory bodies would have a way of calculating the duct size required (there are rules for airbrick size so there must be ventilation standards).

This is sometimes also done to ventilate a subfloor or a disused chimney

Do you have any external cladding or tile hanging? We're north- easterly first-floor tile hung on one side of our semi-detached. Had a CWI oral 'Survey'- they said tile hung areas would be excluded.Offered unencumbered internal access to no avail. Decided not to proceed because unsure if vacant area could create Cold-Bridging causing hydoscopic problems negating any CWI benefits. Now seeking impartial sources for advice.Thanks in advance if anyone could oblige.

how old is the house? sometime tile-hung walls do not have cavities. You can tell by (accurately) measuring the thickness.

The tiles will slightly improve the performance of the wall. If you ever have it retiled you could add external insulation behind the tiles.

In my case, one wall was insulated from indoors due to access. I don't know if you have found an unhelpful installer or if policies have changed.

Internal work causes brick dust so they might have been overburdened with complaints.

Thanks for your input.
Built circa 1977 - Year of the Drought - with cavity behind tiles on blocks in the area with shared semi elevation. Agreed to exonerate installers from any mess issues. Further agreed to empty the room, & assist with heavy duty vac' cleaner whilst drilling, to no avail.
Neighbour's previously installed material later leaked from around a flue & appeared to be paper-mache when blowing around garden.
Whole experience led to our reticence concerning CWI but are willing to reconsider.

If you have a gas fire don't ventilate the flue from under the floor, if the gas fire exceeds 7kw and requires ventilation the regs dictate that it should be taken from within the room, it is not just to aid in flue pull but also it is there for the combustion requirements of the gas fire, if vented from behind under certain conditions it can result in the gas fire spilling products of combustion into the room.

that's useful, thanks

Our house has cwi and damp inside. It grows on lots of walls/ceilings upstairs and I'm just about to go up and wipe it off. Drives me mad. Dehumidifier doesn't resolve it either.

Was the damp present before the insulation as well?

Discouraging for anyone considering CWI ! Have you considered removing an external brick or two to investigate? You could then use a mini camera probe to try & trace the problem. All rather a faff but it would obviously be healthier in the long run to resolve things asap. Could turn out to be something like build up from condensation on uninsulated plumbing - or wind blown moisture via a small gap. Good Luck.

The internet is full of forums and claims from people who had cavity wall insulation retro fitted. @PigletJohn is right but how many houses that age have perfect mortar joints, sealed windows etc. Once the stuff is in it is difficult to remove..

Hi, you are seemingly making some big changes. For better thermal effect the external walls may need some works. I would probably go for injected dpc and line the external walls. Unfortunately, not a cheap solution, however it is effective both in internal comfort and long term energy bills.. Depending on what other measures you are planning, you would do better to have a holistic approach.

Be very careful. Look at support group CIVALLI they've got huge experience of cavity wall insulation problems. Installers don't always check cavities properly, if it goes wrong you have a long battle to get insulation removed and they don't always pay for repairs. If you do go ahead your house needs to be in tip top condition, all air vents need to be sleeved. Check BRE wind driven rain map, if you're in the dark blue area don't do it. External wall insulation sometimes pushed as alternative but has it's own problems. We were sold external but weren't told house needed to be in top condition, installer said it would stop existing rain ingress, it didn't, we're now left with horrendous problems which no-one will take resposibility for despite BBA reporting significant failure due to existing ingress. It's taken our coalman 2 years to get his cavity insulation removed, only after getting a solicitor involved. Cavities were built in UK for a reason -i.e. wet climate.

So, I am in between the severe to very severe on the BRE map. Thank you for that advice, hadn’t come across that before.

Money is tight (single mum, part time job as kids young) hence why I am hoping to take advantage of some of the grants available in Scotland. The CWI is one of them. However... it might just end up being more hassle than it’s worth and I don’t believe any of the neighbours have had it done either. Think I’ll see how the changes are with the new doors/windows and then go from there. I’ve got a massive list of things I still need to tackle but an even longer one of things I’ve already sorted, so slowly but surely I’ll get there.
Thank you so much, everyone, for the sound advice.

Remember an air-tight house is'nt healthy - ensure you spec' permavents in new windows/doors. Some simple things can help improve things too, ie, Ply sheeting & insulation to solid ground floors. Reflective foil behind rad's on external & party walls. Painting backs of same rad's matt black. Utilise 'styrene packaging in the loft area for additional insulation. Grow Ivy, or similar, on external walls & where possible site hedging strategically preventing wind chill to outside walls. Above all ensure you have working Smoke Alarms & CO2 Detectors correctly positioned thro' out your property. Good Luck.

Radiators all on internal walls, got the polystyrene type insulation in the loft already (one of the first things I did!) it’s been brilliant! All windows have blinds plus curtains and I open the windows every day for minimum half an hour, usually more. More efficient heating system and boiler planned for next year and hopefully get the downstairs floor sorted out at some point, too. There’s an actual draft coming from the old doors (blinds in front of them now) so I think it’ll make a big difference. :-)

Do you, or anyone, have experience concerning Solar Panels?They're pushed at you allmost everytime you open up 'tech' down here. There's conflicting info' on brake even & pay back times. Some report they provide warm but not hot water.

In UK, the payback is now so slight that it's only worth doing if you have £6k sitting in the bank earning 0.1% interest, and you have already paid off your mortgage and other debts, fully-funded your pension, ISA, nest egg, insulated your house, and there's now nothing else you can invest it in that gives a better return.

If you have, or can get, a gas boiler, the cost of hot water in the summer is negligible, and solar savings are even less.