Internal wall insulation in Hall Green.

What are Hall Green semis built like?

Most were built between the wars, when British house building was moving from solid walls to cavity walls. That means a Hall Green semi might have 225mm solid brick, or an early cavity that may or may not have been filled. The bays are often lightweight: a timber frame with tiles or render outside and a thin lining inside.

A typical house has a front room and front bedroom with a two-storey bay, a back room and back bedroom, a box room over the hall, and a side gable wall that is fully exposed. Each of those rooms behaves differently in winter.

How do you decide the order for a whole house?

I go through the house with you and look at three things: which rooms you use most in winter, where the mould is and which walls lose the most heat. Then I suggest a sequence.

The room by room guide for 1930s semis goes through each room in detail.

There is black mould in the nursery. What should I do now?

First, deal with what is there: remove the mould safely, wearing a mask, and let the wall dry. Move the cot a little away from the outside wall, keep the trickle vents open and avoid drying washing in the room. Those steps help straight away but will not stop it coming back on a cold wall.

The lasting fix is a warmer wall surface and a steady way for moisture to leave the room. The guide to black mould in a child's bedroom covers this calmly and in detail, and my condensation and mould service explains how I combine insulation with ventilation through trusted trades.

What happens when you insulate the bay?

The lightweight panels are opened up, the frame is insulated and draught-sealed, a board layer goes across to reduce cold bridging through the timber, and the bay is replastered ready for decoration. The reveals and the underside of the window board are insulated too, because that is where condensation usually starts.

A bay starts from about £2,300. In the case study, a bay bedroom wall went from 14.5°C to 18.4°C on the surface, with heat loss through it down by about 71%. More detail is on the Birmingham bay window insulation page.

Can we live in the house with young children while you work?

Yes. I work one room at a time, seal it off with dust sheets and tidy every day. The room being insulated is out of use for several days, so a child might sleep in another room for that week. Plaster needs a few days to dry before painting.

I give you a pre-start guide so you know what to move and what to expect each day. The guide to living at home during internal wall insulation covers dust, noise and timings.

What does it cost and which system would you use?

Internal wall insulation starts from about £2,300 per wall. PIR with PU adhesive is usually £2,300 to £3,000 per wall over three to four days and suits sound, dry walls. A breathable wood fibre and lime system is around £3,000 and about five days, and suits walls with any history of damp.

Each wall comes forward by 20mm to 80mm including plaster. If you have been turned down for a grant, the guide for people who didn't qualify sets out how to do it privately in stages.

Do you travel to Hall Green?

Yes. Hall Green is usually 40 to 50 minutes from Bloxwich, and I plan visits in advance. I also cover Kings Heath and Moseley, Solihull and the rest of Birmingham.