posted by Malachi Chadwick

old homes can conquer climate change

Insulation expert Mukti Mitchell explains how we can bring Britain's draughty old houses up to scratch

Mukti Mitchell tackles your old-home energy dilemmas: Energy efficiency in old homes: your questions answered

Old homes painted in pastel colours

Why are old homes important in solving climate change? What's the scale of the challenge in this area?

There are 27m homes in the UK and only 3m are insulated. Bringing the remaining 24m properties up to modern insulation standards would cut the UK's carbon footprint by a whopping 10% – it's one of the largest single carbon cutting opportunities available.

The difficulty is that half of these properties are over 100 years old, and old properties require specialist skills to insulate effectively while retaining the beauty and integrity of the buildings.  For example it takes more skill and time to effectively and unobtrusively fit secondary glazing to traditional windows than replace them with new double glazing.

But as English Heritage points out, the old windows are made of better timber so will often outlast the new.  And replacing them has a much higher carbon footprint. Another example is that if wall insulation is added to solid walls, if not done correctly it can cause damp and decay between the wall and the insulation.

For these reasons when starting CosyHome Company we decided to tackle the most hard-to-treat traditional properties.  Our reasoning was that post war homes are easy to insulate and loft insulation, cavity wall and double glazing companies are already doing this.  We figured that if we could insulate the most difficult 1% of British homes, other companies will fill in the middle ground and hopefully Britain will be insulated by around 2025.

What are the main insulation methods for old properties?

There are five areas of a house to insulate: lofts, windows, draughts, walls and floors, and each of these areas loses between 10% and 30% of the heat that comes through your radiators.

The solutions are loft insulation, secondary or double glazing, draught seals, internal, external or cavity wall insulation and insulation under or over floors. The only thing that it almost impossible to change in an old property is "cold bridges" caused by window and door frames and joins between walls and ceilings, which is why an old property can only achieve 80% heat savings compared to new build. But that's still pretty good!

What are the issues you see arising most often? Is there any general advice you’d give to people in old homes?

My general advice is take heart, you can drastically reduce heat loss in an old home without spoiling the character of the building. For example, our secondary glazing system is almost invisible from the outside or inside and you can open your windows normally. Old, solid walls do cost more to insulate than modern cavity walls (so you might want to take other, cheaper measures first), but the costs are coming down every year.

The main issues with loft insulation are the materials: you get allergenic reactions to glass and rock wool, and there's considerable embodied energy in the materials. I would recommend sheep wool loft insulation from someone like Thermafleece, which is treated with natural borax to repel pests and lasts four times longer than mineral wool without compressing under gravity. It is biodegradable, low embodied energy, has few allergenic associations and supports British farmers.

For old homes, English Heritage recommends secondary glazing over double glazing for a number of reasons:

  • It retains the old windows which usually have superior, longer lasting timber than modern equivalents.
  • The glass has better colour transmission than modern glass.
  • Keeping something old saves energy -apart from which they look better.

There are various aluminium frame secondary glazing solutions, which work fairly well but are quite noticeable. For this reason CosyHome developed a plexiglas magnetic system that fits onto existing sashes or casement windows. Magnets make it easy to remove for cleaning or painting and because it needs no frame it is almost unnoticeable when in place. The insulation qualities are similar to double glazing and the sound proofing qualities are much better. The main issues with secondary glazing are condensation in the void, arising from water entering from outside through broken putty and condensing on the inside of the outer glass. The solution is to ensure that putty and paintwork is maintained in good condition, which also preserves the windows. Condensation from moist air inside the room is considerably reduced or eradicated by secondary glazing because the moist air no longer touches such a cold surface.

The main issue with draughtproofing is reduced ventilation increasing damp levels in already damp properties.  Hence a good guide is only to reduce draughts by 75%.  But this depends on the property. Try to get an clear idea if you class your property as dry, moderately damp or very damp. Allow more ventilation accordingly. In some properties draught proofing cannot be fitted at all as a lot of ventilation is required to reduce damp. In this case the first step is to look into damp proofing solutions, of which there are various types available. In a dry property thorough draft proofing can be fitted and it is then up to the inhabitants to be proactive about opening windows on nice days to freshen the air.

These three areas are the low hanging fruit of insulation, with high energy savings and financial returns. Insulating solid walls and floors are big subjects, which I look forward to covering in due course.

What advice would you give to people renting old houses?

There are big financial benefits to be had from insulation, and these are gained by whoever pays the heating bills. So it is worth paying for different measures, depending on how long you expect to stay. Payback times depend on existing insulation levels and how warm you like to live, but as a rough guide, draught proofing will pay for itself in a year, loft insulation in two years and secondary glazing in around five years.

There is a good chance your landlord will contribute. The law says that from 2018 rented properties must have an energy performance rating of E or above. So arranging insulation is helping your landlord comply. I would ask a landlord to contribute 50%, which will half the payback time for you and mean you start saving money sooner. You could even try asking for 100% to begin with, but they may feel they need to increase the rent to cover this. A small increase is ok, as your heating bills will go down, unless you decide to live warmer!

How can national and local government help people in old homes?

It would be helpful if the green deal and other grants were to contribute to any kind of insulation including secondary glazing and wall insulation.  Even a grant for a small amount towards the full cost will often incentivise people to pay for the rest.

Councils that pay for a number of case studies in their local area enable techniques to be tried and results to be published.  Householders are much more inspired by seeing a real, working example with their own eyes than reading about it, and much more likely to fund the costs of doing their own home if they know the savings that can be made.

Increased training is also needed.  Seminars run by experts at the cutting edge of the field, for local carpenters and builders will create immediate capacity.  Courses and apprenticeships can be run through colleges to train the upcoming fitters, or thermotechs.  Insulation is going to be a huge industry over the next two decades, so we need to prepare for the rush that will come in the next few years when heating bills have doubled again.


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