Marianne Suhr: Future-proof your home

You’ve probably forgotten how freezing cold we all were last winter; those miserable dark days when the sub zero drafts whistled through our leaky old houses and had us all rooted to our inglenook fireplaces. I have friends who subscribe to the hardy ‘put an extra jumper on’ philosophy, who think that being cold is just the price you pay for living in a gorgeous old house. Needless to say, I rarely visit them during the winter months.

Living in an old house actually doesn’t have to mean suffering falling temperatures, but any improvements to energy performance must be carefully considered. Inappropriate alterations can mean reducing the breathability of your walls, resulting in inadvertent damp and decay. If you have any doubts about a product or system you are being offered, check it out with the SPAB technical advice line before making any decisions.

I was particularly appalled by uPVC window companies who unsuccessfully called for a government ‘scrappage’ subsidy to replace historic windows with plastic equivalents, all under the banner of being green. Plastic windows are without doubt an environmental disaster waiting to happen – in 10 years they’ll be ripped out and put into already overflowing landfill sites.

English Heritage has recently carried out tests to show that simple draughtproofing measures applied to traditional sash windows can reduce air leakage by 86%. This seems to me a more sustainable approach to energy efficiency, not to mention retaining our historic integrity.

Testing times
Before you begin your schedule of energy-saving measures, you should consider testing your house to pinpoint the areas most in need. Draughts can account for the majority of heat loss in old buildings, so start by understanding where the gaps are with an airtightness test. It costs around £250 and takes an hour or two.

A fan is fitted to your front door opening and the house is depressurised. While this is going on, walk around each room and feel around any window or door openings, junctions, loft hatches, downlighters, floorboards, etc, for air being pulled in. It will feel like someone blowing on your finger. Use a sticky note or a pencil to mark the location of every leak so it can be stopped.

Last winter our village borrowed a thermal imaging camera from the council to photograph local houses (hiring privately costs between £300- £400). This can only be done when the weather is very cold and the house is heated to get a contrast between the two. The images show where heat is being conducted through the external envelope. White, red and yellow indicates extreme heat loss – blue areas are those well insulated.

I was fascinated to see how my own house performed following a number of energy-saving measures we had implemented. On the image (left), the window to the bottom right is the only one with no secondary glazing and is losing a great deal of heat. The area above the porch on the first floor landing, shown in green, is the section of wall that was left uninsulated. This indicates poor energy performance compared to the insulated rooms, shown as blue, either side. We have since fitted a thick insulated curtain over our front door to help retain the heat in the hallway.

Good investments
If you’re repairing an old house, now’s the ideal time to improve thermal performance. When it comes to heating, I’m afraid that inglenooks are highly inefficient – the majority of the hot air goes up the chimney and draws in draughts in the process. A wood-burning stove, properly fitted within an inglenook, is four times as efficient, though not nearly as pretty.

If you’re extending a period house, then a wet underfloor heating system provides a gentle and efficient level of comfort. But in order to install it you need to provide a floor slab, a thick layer of insulation plus a screed above.

However, I wouldn’t recommend disturbing an appealing old floor to fit underfloor heating; as well as destroying the floor, it would involve digging at least 300mm and possibly undermining what are probably your very shallow foundations. So do consider the limitations of your old house.

Quick wins
If you’re not planning major alterations to your house, simple improvements will help reduce heat loss and energy bills.

Loft insulation: Hot air rises, so insulating your roof space makes sense. But so many people make fundamental mistakes – for instance, if the insulation doesn’t fit snugly its effectiveness will be dramatically reduced.

If you have a walkway in your loft that squashes down the insulation, or one that is left uninsulated beneath, it won’t perform nearly as well. The very best natural insulation material is sheep’s wool; there are also hemp and recycled paper versions available on the market.

Draught exclusion: Old windows can be the greatest problem area when it comes to draughts, but there are a number of solutions which could eliminate more than 80% of the problem. Wooden shutters can be extremely effective as wood is a good insulator; make sure they fit tightly to minimise draughts. Even thick insulated curtains running from floor to ceiling can make a big difference to heat loss.

Secondary glazing: This is the most efficient way to stop draughts and comes in discreet, slimline versions. Storm Windows offers a bespoke service, to fit any shape or size, and will powder-coat the frame to any colour. For a cheap and cheerful solution, clear polystyrene, which looks like glass but is much lighter, can be used; but it does scratch more easily. DIY Plastics offers a service where you can order the exact size needed and fit your own self-adhesive magnetic strip to the window frame. Although the strip only comes in white, it is very straightforward to paint them to match the colour of your windows.

Magnetic panels in glass or polystyrene can be placed against the window in the winter and removed and stored during the summer. But for windows that need to be opened all year round, try upgrading your windows with draughtproofing – always use a specialist company such as Ventrolla to do this as windows can easily be ruined.

Wall insulation: Beware of insulating your house on the inside walls, as this can cause ‘interstitial condensation’. This is where water vapour travels through the insulation, hits the cold masonry wall surface, and condenses. This can lead to damp problems and mould growth. It’s always better to insulate on the external wall surface if possible.

If you are re-rendering externally, then do consider using a hemp lime insulating render. The hemp fibre traps air to provide an insulating layer and it can also be applied much thicker than a normal plaster to improve the overall U-value of the wall.

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WORDS & PHOTOGRAPHS MARIANNE SUHR
Featured in the June 2010 issue of Period Living