How to Reduce Heat Loss in Your Home
It may not be as glamorous as installing a solar panel, but improving insulation can have just as big an effect. Indeed, in terms of cost-effective ways to reduce greenhouse-gas emissions, making our homes less thermally leaky sits towards the top of the list, alongside cutting back on air travel. Decent loft insulation alone can reduce the annual CO2 footprint of a typical ome by a ton per year and reduce heating bills by a fifth. Wall insulation, though more expensive, can often have an even bigger effect.
Current building regulations state that loft insulation in new buildings should be 20cm. If your current insulation is 10cm or less, you should seriously consider topping it up to the 20cm level, and possibly adding even more. If you want a grant to install a renewable-energy technology, you'll need at least 27cm.
It's well worth exploring the various grants available for loft insulation. If you can afford it, however, you may want to forgo any grants and opt for the greenest possible insulation materials. As a rule, standard mineral-based materials use more energy and chemicals in their production - and are less likely to be locally sourced - than those that use natural materials such as wool or flax. The latter, though often more expensive, allow for better circulation of air and help to avoid the retention of toxins in a building, linked by some to "sick building syndrome".
Most houses built in or after the 1930s have cavity walls - an inner and outer wall with a gap in between. You can usually spot cavity walls as they're relatively thick: around 30cm, compared to around 23cm for a typical solid wall. The pattern of the brickwork can also be a useful clue. With cavity walls, each brick is equally wide, whereas with solid walls many bricks will be placed sideways on and appear half as wide.
If you've got cavity walls
If your home has cavity walls, then making sure the cavity is full of insulating material is a no-brainer. Filling an empty cavity can lead to huge energy savings for a fairly small initial outlay, and it's a quick job that causes minimal disruption. Holes are drilled in the building's exterior wall and insulation material, which can be foam, mineral wool or some other option, depending on your budget, is injected into place. If you're not sure whether your cavity walls have already been insulated, then look for small circular marks left by the drilling process. Alternatively, ask a local insulation service to come and take a look. Note that there are many homes which have cavity walls that are unsuitable for filling. If yours if one of them, consider solid wall insulation instead.
If you've got solid walls
Around a third of homes were built before 1930 and have solid rather than cavity walls. It's generally more costly and labor intensive to insulate these kinds of walls, though it's perfectly possible and may well be the single most important step you can take to reduce your homes footprint.
The main decision is whether to go for external or internal insulation. The internal option involves adding insulating material to the inside face of the exterior walls - either boards within a narrow wooden frame or a flexible material known as Sempatap. The latter is rolled on almost like wallpaper, can be decorated with any finish (emulsion, wallpaper or even tiles) and has the benefit of combating condensation and black mould.
Internal wall insulation will of course reduce your room sizes, though if you use Sempatap you'll lose only 1cm along the length of each affected wall (usually one or two walls per room). The typical cost will be around $45 per square metre, plus the price of redecoration. At this price it might take more than a decade to repay the initial outlay. However, DIY enthusiasts can save money by doing the installing themselves, and it's also possible to cut the upfront cost by insulating only the most frequently used (or the coldest) rooms.
By contrast, external wall insulation involves paying someone to add a thick layer of insulating render - up to 10cm deep - to the outside walls. This can be very pricy if done in isolation, though if you need to repair the walls anyway, then the marginal cost may be as low as $1800 for a medium-sized home, in which case it might pay for itself in just five to six years. Of course, exterior insulation will drastically change the look of your building. In conservation areas this may rule it out completely. Elsewhere, you'll need to balance the energy savings with aesthetic concerns. The final finish can be flat (wet render), pebble-dashed or, for an extra cost, clad in wood, brick slip, clay or aluminum.
External insulation will typically produce slightly better energy savings than the internal option - though the difference is fractional.
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