Hi All,

Let me introduce myself. Recently bought a large late-Victorian detached house (Accrington brick), with Cavity walls *I think* - (I know it is lame not to know but I'm out of the country just now - I was initially sure it was cavity wall because of the airbricks around the perimeter at low-level but I'm now aware that airbircks are present on solid walls for the void beneath the floating floor.

The ground floor is just over 2000sqft and the ceiling height is 3.7 metres. The current heating system is old rads running off thick pipes on show in all of the rooms - the house hasn't been touched since the 70's

At this point we are in the process of deciding on a heating option. Everybody from prospective tradesmen to family members have all commented on the fact that it will cost a fortune to heat. From reading the discussions it seems we need to insulate.

We are converting the loft and so will insulate according to current regs. Regarding the external walls I was leaning towards CWI (assuming there is one!) until I started digging a bit deeper and I'm now concerned about potential damp problems. I am also looking at IWI but again, from reading this site there could be problems with spalling. We are on a slightly elevated site, so I suppose there is a susceptibiity to driving rain. There are areas of damaged brick (generally around where pipes have leaked and below around 1 metre).

My other concern is that there are a lot of original internal features (mostly ornate ceiling beams and architrave around the windows (no paneling)) and I'm not sure if we could work around everything with IWI, I suppose we could look at 'blending the wall in' i.e. sloping the stud back to the original wall as it approaches the window - this may look seriously strange!

My heating preference would be GSHP or ASHP with underfloor heating. I understand the principal of UH working to a lower temperature and wonder if UH is realistic in an old victorian house, especially considering the height of the ceilings?

Other info, all windows will be either replaced or refurbed/reglazed sash windows. We will be repointing all the brickwork. Building isn't listed.

My questions are these:

1. Insulation - What is the best option?

2. Would it be very risky to IWI with reference to the slightly elevated sites?

3. Are there minimum coverage thresholds for IWI or would leaving areas without IWI (i.e. areas leading up to windows etc.) seriously compromise the IWI?....or, if not, - to quote Keven McCloud - look Frankinsteinish!

4. If we have to go with CWI would it be enough for UH with G/ASHP to work to provide comfortable heat.

BTW....we don't want to EWI as will ruin the character of the building.

Thanks in advance for any help and suggestions!

Loads to say re IWI, and various options to look at, especially in the light of the already-spalling brickwork. I haven't re-read JMS' thread, but have, of late, seen very few Victorian cavities where CWI contractors have agreed to fill.

At this stage, though, I will concentrate on the roof. Please consider not just ''insulat(ing) according to current regs.''. You could do better at relatively small marginal cost, and you only get to do it once. Sure, if headroom is a problem, you have to compromise, but there's often no reason not to look for U values of 0.1-0.13 instead of 0.16 on flat surfaces, and absolutely no reason to adhere to the ('soft' ) standard of 0.3 on stud walls to eaves voids, for example. A spaced stud wall is easy to contruct so that your entire loft (excl windows) is wrapped in a 'blanket' at better than 0.16.

Good luck!

Oh, and I forgot air-tightness. Everything filled, foamed taped and tight as a drum!

''can you 'fade' (no idea of the building term for this) the stud wall back in back in to meet the original wall or at least original wall with say a layer of 'magic' wallpaper/plasterboard as you approach original features?''

Well you can..... Whether or not you should is another issue. I would heartily advise against it if there is any other way. Diminution, yes, if you have to. Virtual cessation, no. can you give us more idea of what you are up against?

And re the cavity, how wide is it? CIGA (cavity insulation g'tee ass'n) generally require 50mm, and I have seen 47mm refused! A lot more issues though that they don't like with Victorian cavities... Lack of DPC, risk of damp ingress, lumps of crud, rotting ties....

My understanding of filling a Victorian cavity which was build up researching the issue (i.e. I'm not a professional) is that there is nothing per se wrong with doing it if the cavity is good but cavities were not standardised before the 1930/40s. This means that a Victorian cavity could range from great to appalling and so no one really wants to go out on a limb and fill them as the chance of come back is so much higher.

Some of the problems (to some extent as with any full fill cavity) are:

Cavity width – most fitters want 50mm to get a decent fill
Rising damp/poor DPC – are the leaves of the cavity dry (i.e. damp meter dry), is rubble in the bottom dusty – good sign, is the dpc in good nick or disintegrating?

Penetrating damp (i.e. Driving rain) – see sinner boy’s driving rain building regs reference in previously linked thread plus common sense (i.e. are you on an isolated hill or in a town) and overhang of eaves. Do you have lime mortar (good) or has it been repointed with cement based mortar (can trap moisture in the outer wall).

Wall tie corrosion – tell tale sign is something (rust is bigger than iron) pushing bricks apart although you need to find a few ties and take them out. I can’t remember the exact criteria but a bit or corrosion is normal – you basically want the tie OK over most of its thickness.

Condensation – defects in the cavity/lintels/cold bridges turn a border line condensation into black mould on patches of wall associated with the cold bridges. This is probably the easiest to fix through ventilation.

We were good on all fronts (especially as condensation is thing of the past with MVHR) so decided any risk was probably lower than a 1940s cavity and have no regrets. The house is warmer in the winter and cooler in the summer and no issues have arisen.

Hope that covers everything!

In your case if you have spalled bricks this may be indicative of excess moisture in the outer leaf of the cavity so I would tread with care.

If you have flemish bond then given a standard brick length (today) of 215mm your walls not including plaster are likely to be around 330 thick if a cavity is present and 215 thick with no cavity. (Bricks weren't standardised at the time of your construction so it could be different). It would be usual to fill the cavity with what is called a 'half batt' brick. Additionally if you have proper flemish bond there is no way you will get cavity wall insulation in there.. too many obstructions. Wikipedia has a nice little diag to show you in plan and elevation how flemish bond works. http://en.wikipedia.org/wiki/Brickwork#Flemish_bond