Determining boiler size from serial number

[Andrew]

An early 70's house (detached?) will have almost no effective insulation at all, except perhaps a thin layer of loft insulation. It may have had replacement DG during its lifetime, and some more loft insulation, but it will be the heatloss through the walls and (?solid) ground floor that is the issue.

A combination of cavity wall insulation (to stop air movement inside the cavity) as well as external wall insulation is probably the thing to spend your money on. The original house will have a cavity that is only 50mm or 65mm, so filling that will only offer marginal improvement (unless there is significant air movement through the cavity). In Scotland there is the issue of driving rain, so cavity insulation on its own might have unexpected downsides. Adding external wall insulation as well will add a new external rain skin because of the extra render.

That leaves the (?solid) ground floor which might be fixable but that involves digging out the screed and replacing with PIR between battens screwed into the slab and a new timber floor. If the screed has sufficient depth then you might be able to consider underfloor heating but this is highly disruptive and costly, unless you can diy it. External wall insulation would only need outside pipework to be relocated.

[Theo]

It is highly likely that a 70s house will have had cavity wall insulation installed by now, in the 90s if not before.

Just doing a cavity fill isn't perfect, but a lot better than nothing - much more than marginal.

An unfilled cavity wall has a U value of about 1.6, when filled it's about

0.3. So reduces the heat loss by 80%.

That and loft insulation are the easiest and cheapest to do, if you haven't already.

An uninsulated floor contributes about 10% of your heat loss. For many people the costs of redoing a solid floor means this isn't worth chasing. A simple way to insulate is carpets with good underlay - it's not in the same league as PIR, but if you're installing carpets anyway then it helps.

Theo

[Spike]

There are a number of firms that specialise in cavity-wall insulation removal, which isn’t a cheap exercise, and there’s also the Cavity Insulation Victims Alliance who try to get some form of justice for sufferers of mis-sold CWI.

CWI is not a universally-acceptable procedure.

[Theo]

Agreed it's not an panacaea, but I'd have thought a 1970s brick+block construction would be relatively uncomplicated? It's not into lime mortar and breatheable paints territory.

Theo

[Spike]

I did see a map somewhere that showed that large parts of the UK were unsuitable for CWI due to the threat posed by heavy driving rain. IIRC the whole of Wales and the South West were one such area.

[Theo]

I'd have thought that could be addressed by sealing the bricks from the outside, so there's no water penetration by the rain. A lot of properties in eg Wales and Scotland are painted or rendered which takes care of the sealing.

This is Ireland, which is known for being moist:

"3.5.2.1.2 Severe Exposure Severe exposure to wind-driven rain applies in districts where the driving rain index is

5m²/sec/year or greater (see Figure 2). In severe exposure areas the type of outer leaf masonry finish where the Rockwool Blown Cavity Wall Insulation System is suitable is:

• Impervious cladding and rendered walls with a minimum cavity width of 50 mm and up to

12m in height.

• Walls must be in a good state of repair with no evidence of frost damage and no evidence of damage which would cause water ingress. Unrendered brickwork is not suitable for full-fill cavity wall insulation in the severe exposure zones"

(in other words, sounds like the usual story of cowboy installers and then ambulance-chasing removals firms)

Theo

[Spike]

Ah…the map I mentioned can be found here:

[Theo]

Yep, that page is talking about new builds rather than retrofits (hence cavity sizes are something you can control at design time), but it does make the point that rendering or cladding can allow you to have a full cavity because there's now an impervious layer to stop the bricks getting wet, and so the drying function of the cavity isn't needed any more.

(in other words bricks are a poor rainscreen and better to have a rainscreen which is designed for that job in front of the bricks)

Theo