Internal wall insulation in Sutton Coldfield, designed around your wall.

What is internal wall insulation, and will it make my room warmer?

Yes, in most cold solid-wall rooms it makes a clear difference. Internal wall insulation (often shortened to IWI) is a layer of insulation fixed to the inside of an external wall, finished with plaster so the room looks just as it did, only warmer.

Many homes in Sutton Coldfield, Great Barr and Walsall were built with solid brick walls and no cavity to fill. The heating goes on, the air warms up, but the walls stay cold and the room never feels settled. Insulating the inside of those walls is often the most practical way to change that without touching the outside of the house.

People usually tell me three things afterwards: the room warms up quicker, it stays warm after the heating goes off, and it simply feels more comfortable to sit in. That comfort is the main reason most of my customers get in touch, more than the bills.

Why does a solid-wall room feel cold even with the heating on?

Because the wall itself is cold, and your body loses heat to cold surfaces around it. Warm air alone cannot fix that.

A useful way to measure a wall is its U-value: how easily heat passes through it. A lower number means less heat escapes. An uninsulated 225mm (9 inch) solid brick wall is roughly 2.0 to 2.1 W/m²K, which is poor by modern standards.

As a simple illustration, bringing a wall from 2.0 down to 0.5 W/m²K cuts the calculated heat loss through that wall by 75%, with the same temperatures inside and out. The real figures depend on your wall and the system chosen, and the saving on that wall is not the same as the saving on your whole heating bill.

There is also radiant heat loss. Sit next to a cold wall and you lose warmth to it, a bit like standing near an open fridge. Turning up the thermostat helps for a while, but it does not change how well the wall holds back heat. Warming the wall surface does. My guide on why a house feels cold explains this in more detail.

How do you decide which insulation is safe for my wall?

I look at the wall first, then model how moisture will behave before I recommend anything. The wall decides the system, not a price list.

At the free home visit I check the construction, the condition of the brickwork and pointing, any signs of damp, the existing plaster, how exposed the wall is to driving rain, and how the house is ventilated. I also ask how you use the room and what you want it to feel like.

I am a qualified Retrofit Assessor and Domestic Energy Assessor, so this part is my job, not an add-on. With that information I run moisture (hygrothermal) modelling. It predicts how heat and water vapour will move through the new wall build-up over the seasons, so I can choose a system and a thickness that keep the brickwork able to dry out.

If the survey shows a real damp problem, such as broken pointing, a leaking gutter or bridged ground levels, that gets fixed first. Insulation should never be used to hide a defect.

Breathable or PIR insulation: which is right for my wall?

For most traditional solid brick homes I prefer a breathable (vapour-open) system, but PIR has its place where space is tight and the wall suits it. I fit both, and I will explain why I recommend one over the other for your home.

Breathable systems let water vapour pass through, so the wall keeps its natural drying routes. Government guidance on internal wall insulation generally favours this approach for traditional solid walls. PIR is a rigid foam board that insulates very well for its thickness but stops vapour, so the detailing has to be very careful.

A natural board alone does not make a system safe. The adhesive, base coat, plaster and even the paint all need to be vapour-open for a breathable wall to work, so I specify the whole build-up, not just the board, usually finishing with lime plaster.

How much room space will I lose?

Usually between about 20mm and 80mm off the wall, including plaster. On a typical bedroom wall that is less than you would notice once the furniture is back.

PIR systems are the slimmest. Wood fibre and cork need a little more thickness for the same performance. Sometimes I use different thicknesses on different walls, as I did in this 1930s bedroom, where a thinner board next to an en-suite door avoided having to alter the doorway. I will mark the finished wall line during the visit so you can see exactly where it will sit.

What happens to my sockets, radiators and skirting boards?

They all come off, and they all go back, neatly, on the new wall surface. This is where a lot of the care goes, and you do not have to arrange it yourself.

• Sockets and switches: brought forward to the new surface with deeper back boxes, organised with a trusted electrician.
• Radiators: taken off, then re-hung on fixings that go properly into solid support, not just into insulation. If a bigger radiator makes sense, the plumber can swap it at the same time.
• Skirting boards: carefully removed and refitted. Original or decorative skirting can be saved and reinstated.
• Window boards and coving: extended or refitted to suit the new wall depth.
• Curtain poles and shelves: I will tell you where the fixing points are, so nothing hangs off insulation alone.

If you want me to, I manage the whole project: electrician, plumber, joiner and waste removal. You deal with one person.

Why do window reveals and junctions matter so much?

Because that is where cold spots and mould come back if the job is rushed. A wall can be well insulated in the middle and still fail at the edges.

The places I pay most attention to are the window reveals, the corners, the floor and ceiling edges, and where internal walls meet the external wall. Reveals often only have room for a thin board, but even a thin layer lifts the surface temperature where condensation usually starts. Board joints, edges and pipe or cable holes are sealed so the insulation is continuous.

Once the plaster is on, all of this is hidden. That is why I explain it before you compare quotes: two prices can look similar while the detailing behind them is very different.

Will internal wall insulation stop condensation and mould?

It removes one of the main causes, the cold wall surface, which often makes a big difference. But ventilation still has to do its job.

Condensation forms when warm, moist air meets a cold surface. Insulation warms the surface, so there is less chance of water settling on it. Everyday moisture from cooking, showers and drying clothes still has to leave the house, and even a breathable wall does not replace fresh air.

Where it is needed I recommend trickle vents, door undercuts, extractor fans or heat recovery ventilation, and organise them with trusted trades. You can read more on my condensation and black mould page.

How much does internal wall insulation cost in Sutton Coldfield?

From about £2,000 per wall. A PIR system is typically £2,000–£3,000 a wall and takes 3–4 days; a breathable system is around £3,000 and about 5 days.

The price depends on the size of the wall, the number of windows and reveals, the system, what needs moving (radiators, sockets, skirting) and whether the old plaster has to come off. After the home visit you get a clear written quote with everything listed, so there are no surprises halfway through.

Funded schemes such as ECO4 exist for eligible households, and they can be a good route for some people. My work is for homeowners who want the system designed for their particular wall and finished properly, and who are happy to pay for that care.

What is it like having the work done?

Calmer than most people expect. The room is out of use for a few days, the rest of the house carries on.

Before we start you get a pre-start information guide, so you know what happens each day. We cover floors and protect furniture, keep the work area tidy at the end of each day, and I walk round the finished room with you at handover. The walls are left plastered and ready for you or your decorator. About four weeks later I call to check how the room feels. For bay rooms, see bay window insulation.