Heat losses caused by draughts are effectively, easily and cheaply eliminated with efficient draughtproofing. Of all the forms of home insulation, draughtproofing brings with it the most quickly noticed improvement in personal comfort—and immediate savings in fuel costs.
Research has shown that up to 15% of all household heat losses are attributable to this persistent and niggling fault. Many other forms of heat insulation—and therefore heating— are largely wasted if draughts are present nearby. The most noticeable problems occur in the main living areas of the home.
In any room, a badly fitting door or window is likely to be the main offender—but less obvious sources of draughts can be significant. A weakly-sprung letter-box flap, cracks in brickwork, and gaps caused by collapsed mortar around door and window frames, or gaps in the siding or weather board of a timber clad house, all contribute to heat loss.
In a centrally-heated home these draughts may not be as noticeable as those in a house with single-room spot heating where draughts combine to produce cold spots. For reasons of economy it makes sense to try and eliminate the problem. In most cases, the job is not too difficult.
The causes of draughts
Draughts are mostly the result of air pressure differences within a house but they will also occur wherever there is a large gap to the outside, or between a cold and a heated room such as hall and sitting room.
Convection currents are the main cause of air pressure changes, however slight, and the effect can extend from a single room to a whole house. In a single room a large expanse of cold single-glazed window often gives rise to cold down-draughts , even if the whole room is sealed off as a unit. More usually, this cold window down-draught combines with seepage around doors and cracks to make living conditions very uncomfortable.
A greater problem is caused by an open-grate fireplace or, indeed, any fuel-burning appliance with a single chimney flue to the outside. Room air is required for the combustion process. This—and the fact that additional heated air rises up the chimney along with the fumes—creates a partial vacuum in the room which encourages incoming air seepage through gaps around ill-fitting door and window frames.
If there is any doubt about their whereabouts, the. job of locating draughts is best done on a cold and windy day. Use a bare candle flame to detect the slightest movement of air. If you have one, a smoking taper will give better visual indication and is safer.
Hold the candle flame or taper close to suspect areas around windows and door frames, watching carefully to see which way the smoke is drawn. Also, check through-wall fittings and pipework where filling looks to be in need of repair.
If possible, seal each area as you proceed. Work from room to room, taking in the hall and other connecting areas as you go.
When draughtproofing each room do not forget to allow enough ventilation for any fuel-burning appliance that may be in use there. Even if a ventilator grille is provided, this may be positioned badly in relation to the appliance. Consider repositioning the grille closer to the appliance to reduce cold draughts across a room. A ventilator grille can be let into suspended flooring or into a nearby external wall.
Building and safety regulations insist on suitable arrangements for ventilation of fuel-burning appliances and this point must be considered in any project that involves extensive draughtproofing.
Sealing doors and windows
Sealing doors and windows accounts for most of the draughtproofing that is likely to be needed. Though in each case the job can be simple and inexpensive, better looking fittings are available at greater cost.
At the cheapest end of the scale of proprietary draught-excluding products is strip-plastics sponge, attached to a self-adhesive backing and cut to length off a supply reel. With the backing peeled off, the sponge strip can be stuck in place on the cleaned contact surface between a door or window and its frame.
Strip-plastics sponge is an effective draughtproofer—providing it is used around the whole frame. However, it does tend to get dirty and tattered, and may disintegrate if exposed to damp and sunshine for any length of time. The wipe-clean surfaced type should last longer but is more expensive.
Perhaps as cheap—and certainly more effective when used in old, warped or rustic frames—is one of the new-generation of mastic-like sealants such as silicone rubber. Squeezed from a tube in a continuous, even length along the contact area between window and frame , it acts as a rot-proof barrier against moisture and draughts.
Though the sealant is flexible enough to take up the irregularities of the frame and window, it can be removed when required. Allow up to a day for it to dry completely, although windows can be shut after just a few hours.
Rigid strips of polypropylene, vinyl, phosphor-bronze or aluminium can be used in place of foam strip. Though no more efficient, these sprung, hingelike strips do last indefinitely and are a better proposition on doorways to the outside.
Cut to length and tacked in place round the door or window rebate the strips are easily fitted. As the door or window is closed the two halves of the ‘hinge’ close together— one side fixed to the door frame, the other sprung against the door.
The plastics types should last as long as their equivalents in metal and are easier to fit. though special aluminium strip is necessary for metal-framed windows. The metal ones have ready-punched fixing holes. All types of hinged strip can cause jamming if fitted to an already tight door and frame, in which case foam strip would be better.
Secondary-sash double-glazing also acts as a fairly efficient draught-proofing aid for windows but ought to be used in conjunction with excluding strip in order to prevent undue condensation build-up when it is fitted.
Mastic can again be used for making good small gaps between a door or window frame and the accompanying brickwork where the filler mortar has crumbled. But purpose-made cellulose, or vinyl-based filler is cheaper and usually easier to apply.
Take a particularly close look at the underside of window sills—especially large ones such as those found in some types of bay window—and check for draughty gaps there. Use cement or filler to seal these.
Even the finest of cracks can still let in a powerful draught if the conditions are right. In this case, an inconspicuous fillet of wood filler may be all that is required.
Timber clad houses
One source of draughts in timber clad houses is the inevitable gaps between the weatherboard, clapboard or shingles sections, and between these materials and door and window frames. These gaps should be filled with an appropriate mastic —these days, often silicone. Clean out the old caulking, and wipe the area with a rag soaked in white spirit, turpentine, or other solvent. Caulking is available in disposable cartridges, and is forced into the gap using a cartridge gun. Make sure the bead of caulking adheres to both sides of the joint. Very deep or wide gaps may need some packing out first.
There are many types of draught excluder for the gaps under a door.
Strips of inexpensive rubber or plastics draught-excluder about 30mm wide can be screwed or tacked to the lower edge of the door on one or both sides. But these tend to wear quickly, especially if positioned too low and hard against floor covering. Position each strip so that the edge just indents, or is bent by, the floor covering against which it rests.
A better long-term proposition is a metal door sill and door seal arrangement fixed to the outside of the door. A weatherproofing shield can be fitted instead of this to protect a sill fixed to the floor.
Better for inside the house—and well-suited to sliding doors—is the brushpile type of strip, the bristles of which compress to form a very effective seal. This can be used in conjunction with full carpeting in most instances, but is particularly suited to polished wood or tiled floors. When fitting, adjust the strip so that the fibres are very slightly bent when the door is closed.
Another solution is to use a ‘rise and fall’ excluder, particularly where a hard object—such as a door mat— has to be crossed. In this case, adjustable strip with an angled striking face is kept in place by a hollow moulding attached to the base of the door. In the closed-door position, the strip self-levels. As the door is opened the strip is forced up- wards as its angled face strikes the floor covering.
At the other extreme, a substantial gap of more than 20mm ought to be built up to reduce the eventual gap between the fitting and the base of the door. Threshold strips provide a partial answer, but you may find that these have to be fitted over thin battens to fill the extra space. Battening used on its own and covered by carpeting can also act as an excellent seal and this inexpensive idea is well worth considering. Use padding in the form of offcuts of carpet to build up either side of the batten before laying the main carpet over.
Dealing with other draughts
Bare floorboards may look great, but they can also be a source of strong draughts which you cannot afford to neglect. The tongued-and-grooved types are designed to get round the problem but even so, some joins—especially those near the skirting—may need attention. The worst offender is the old, square-edge boarding. Here, even fitted carpet is not always completely successful at excluding draughts.
The best solution is to fill the gaps between the boards, either with one of the proprietary mastic-like compounds described above or with papier mache.
When using filler, smooth it into each joint with a piece of electrical flex. If you decide on papier mache, use a wood stain to match it to the colour of the floorboards.
If skirting boards are the problem use fillets of mastic, filler paste or cement as necessary. The gap between the skirting and floor boards is a common source of draughts and can usually be eliminated by wall-to-wall carpeting.
If suspended flooring is being installed or repaired, or if you have crawl space under the house, you can prevent quite heavy heat losses by insulating between the joists. There are two kinds. Paper-faced glassfibre batts , commonest in Britain, have flanged edges for easy stapling to the joists. Foil-backed batts, common in the US and Canada, are rammed between the joists and held in place by wire mesh stapled to the bottoms of the joists. The foil vapour barrier must face upwards.
Make sure the loft trap or attic door is treated in the same way as others using the same methods of draught-proofing. If the loft area has been properly insulated, overlapping material at the edges of the door normally provides a good enough seal.
Then there’s the letterbox. Here, you can fasten a piece of rubber or old carpet to the inside of the flap. But for a better-looking job, fit a stronger spring and line the slit with foam strip, or exchange the old flap for the new type with brush inserts. Another type fits behind the flap and is easily screwed into place.