Above: BBM’s The Nook Eco-retrofit was a great success in terms of achieving an eight per cent carbon reduction in heating energy requirements but it wasn’t cheap. When it comes to low carbon refurbishment it turns out there is a huge variation in the cost and difficulty of treatment from one building to the next. Image: © BBM Sustainable Design Ltd.
Again this week I met a couple that had recently bought an older house that they were finding intensely cold and very expensive to heat. They had recently bought the property and this was their first winter in it and yes, they were wearing very thick jumpers. They had a £100K to spend on refurbishing and making it energy efficient but to my eye I realized immediately this house was not cheap to treat and would probably never be truly cheap to heat. If you want an existing property that is both cheap to treat such that you make it cheap to heat, you better look with a discerning eye. Here are my top tips:
Don’t stretch your budget too thinly
It is fair to say that the most common enquiry an architect will receive in the private residential sector is a couple who have bought a house and they want to add an extension and they want to make the rest of the house more energy efficient. Nine times out of ten, their budget will be insufficient to do both elements well and normally they end up just making the extension and the house remains expensive to heat. Would it not be better to find a house big enough for your needs and then plan a really good energy efficiency refurbishment that you can afford? I think in the energy starved future ‘adding value’ to a house in real estate terms will not just be about how many additional rooms you may have added but to demonstrably show how energy efficient and cost effective the building is to live in.
The less surface area the better
The humble mid-terraced property is your best bet because you simply have less external wall to insulate. However be careful of terraced housing with large rear extensions – with their shallow narrow but long floor plans and lots of external walls they are particularly parky in winter.
Steer clear of charming but fussy architectural detailing
If the property has lots of charming but fussy architectural articulation, this will likely be expensive to deal with when it comes to insulating the walls. If it is on the outside you may also find the local authority are not too keen on you changing it or covering it over. If you are insulating on the inside, you may override the charm of the period features.
Eek out a timber frame
Importantly for a refurbishment, it is usually easier to carryout an energy efficient refurbishment on a timber frame building than on a masonry one and the key to that is ensuring you keep the constructions BREATHABLE. However in the UK there has been a lot of predominantly unwarranted resistance to the establishment of a modern timber frame construction. It is true a lightweight timber frame building can be prone to overheating if the glazing is poorly protected against too much unwanted solar gain and/or the structure is under insulated. That said it is quick and easy to heat up.
There are a lot of people who espouse the benefit of heavy thermal mass when it comes to energy efficiency – solid brick, stone, blockwork or concrete will give you that. The idea being is that once you’ve loaded up the internal fabric with the heat energy or ‘coolth’ to provide thermal comfort, the building will not be too much affected by big fluctuations in outside air temperature between day and night. Of course this also means you have to insulate to the outside of the mass really well so your building does not hemorrhage the energy. This has to be taken with moderation. Too much thermal mass will give you internal condensation issues, particularly in the warm season – counterintuitive tough it may seem. It will be interesting to see what the insurance industry makes of poorly conceived eco-retrofits of traditional brick buildings relative to well designed timber framed houses in the years to come.
Avoid buildings where internal insulation is the only allowable solution
When it comes to insulating external walls it is always more efficient and safer to insulate on the outside of a property than on the inside faces. If you insulate the inside faces you will have the risk of creating stale moisture behind the cladding and this may lead to mold growth and possibly fungal attack of the building fabric. Conservationists should take note that if you insist on a brick or stone building being insulated internally, that stone or brick will stay colder and wetter for longer with an increased rate of frost damage. If you have timber joists socketed into the brick, these should be cut back and the load transferred to the sidewalls and that is expensive to execute. The best type of internal insulation is a breathable one. If you can get the moisture in the wall to transpire to the inside as well as the outside, it should be safer. The only other watch point is not to insulate internally too much. Super insulating on the inside of a masonry building will increase the risk of defects arising. The aim should be to just to take the edge off those ‘stone cold’ surface finishes. Calcium silicate boards, mineral quilt and cork linings can achieve just that.
Hunt for a property with plenty of access to the sun
If you want to take advantage of free energy from the sun, look for a property with plenty of sun. A south-facing slope with little overshadowing buildings or trees is ideal. Also check how the building is orientated with the sun. If you have large amounts of glazing facing south then you can look forward to plenty of free passive solar heating in the colder months. South facing glazing is also easier to protect against too much solar gain in the warmer months with external blinds, shutters or even foliage. East and west are tricky as the sun is lower in the sky. Large amounts of west facing glazing are perhaps to be avoided or changed. Check out the roof and make sure it can accept plenty of solar panels with minimal overshadowing and predominantly facing south. Hips, dormers and chimneys are not great when it comes to an efficient array of solar panels.
Climate change adaptation
The experts say our weather patterns will change quite significantly over time. There will be longer and more intense periods of sun and rain that in turn will stress a building’s fabric yet further. Older buildings may yet perform better than some of our more recent commercial offerings particularly in protecting the occupants against unbearable overheating. If many of our houses then require energy for comfort cooling in the summer as well as for heating in the winter, our efforts towards creating cheap to heat buildings will be environmentally meaningless.
Avoid deep floor plans
Why is it so many people want a large extension that makes for a really dark interior? Once you create spaces much more than say five metres away from a window, you end up with dark interiors and having to have lights on most of the time. You lose a sense of well being in such spaces. In such instances maybe consider the motto, ‘less is more’ or ‘small is beautiful’. Clever design can of course make even small spaces a joy to be in.
The golden egg of eco-retrofits
With all the above in mind, what you really need to find is a timber framed mid-terraced house with no back extensions, a good expanse of glazing facing south, little or no neighbouring overshadowing and a well designed floor layout affording good daylighting levels inside.
Ian McKay Dip Arch RIBA