Insulation and Draft Proofing

Updated: Mar 31


Insulating and draft proofing your home well is one of the most cost-effective measures households can take to reduce household fuel consumption. It is also an important factor in allowing eco-friendly household heating and hot water solutions to efficiently replace traditional non-eco-friendly ones. The only grant available is the ECO grant (indirectly via your energy supplier). From a cost perspective, even without a grant insulation represent a low cost to starting the journey to a greener home.


Draft Proofing and Lagging

There are many simple yet effective ways to significantly reduce heat loss, in turn lowering your energy consumption, and heating bills. These measures can typically be achieved without professional help, and they will pay back in under two years. Lots of professional help is available should you prefer but payback time will be extended as labour charge will be a big part of the cost.


Draft Proofing

Draught-proofing is one of the cheapest and most effective ways to save energy. Put simply you should block up unwanted gaps that let cold air in and warm air out. It is of course essential that your house is still correctly ventilated to prevent unwanted condensation or damp. Typically, modern windows and doors will have draft exclusion “built in” so whilst at the DIY store, take a look at them as an example of what you are aiming for.


Assuming you do not already have such windows, you will need draught-proofing strips to stick around the window frame and fill the gap between the window and the frame. These range from simple self-adhesive foam or rubber tape through to metal or plastic strips with brushes or flexible blades attached. Typically, the self-adhesive tape will not last as long but is cheaper. Make sure the strip is the right thickness to fill the gap in your window as they do come in different sizes. For sash windows it’s best to fit brush strips.


A very similar approach can be taken with gaps around the edges of external doors by fitting foam, brush or flexible blade excluders onto the frame. Often the largest gap with be found at the bottom of the door and specific brush or hinged flap excluders are available for this purpose. Also don’t forget the keyhole, for which metal/ceramic covers are available or the letterbox, for which hinged flaps and brushes are available. Only consider draught proofing internal doors or hatches if they lead to a room you don’t normally heat, such as a loft or spare room. First, simply keep those doors and hatches closed when not in use. If there is a gap at the bottom of the door, block it with a free-standing material tube draught excluder. These are widely available for purchase but can be easily made from spare material filled with non-recyclable bits of plastic/foam waste. Hatches can benefit from the installation of draft excluders in much the same way as windows.


Finally, and if you have one, do not forget your chimney. Chimneys, by design, draw warm air out of your home. If you do not use your fire place for heating, which we would recommend, as currently no eco-friendly solution exists for this, then there are two options available. You can seal your chimney from the base cheaply by fitting a cover over the aperture in the hearth. These come ready made or can be custom made, are not expensive and relatively easily fitted. Alternatively, your chimney can be capped at the top, which will also help prevent weather and animals entering the stack, but it will be more expensive as it will require professional fitting. If you do intend to use your fire and your hearth does not include a “closing mechanism” then temporary fabric based or inflatable solutions are available, but be sure they are removed before the fire is used.


When fitting these draft-proofing measures take time to be sure you have the best coverage and fit possible. It is also worth checking the quality of installation of windows, vents, piping and skirting boards as poor installation or the effects of time may result in noticeable drafts. Re-caulking will normally solve this, although you may well want to involve a professional depending on how comfortable you are with DIY. As mentioned, air does need to flow in and out of your house so it stays fresh, dry and healthy. Make sure you don’t block or seal any intentional ventilation, including: extractor fans, underfloor grilles or airbricks, wall vents or trickle vents in modern windows.

Caulking windows for winter
Copyright: AndreyPopov

As mentioned these measures are worth it for energy saving purposes alone, and will pay back many times over for most, but also your living space will simply be more comfortable without the drafts.


Lagging (Water Tank and Pipe Insulation)

Lagging water tanks and related pipework will reduces the amount of heat lost by your heating system to unintentional spaces making it more efficient. Again, this should reduce energy costs and carbon footprint, pay back rapidly and is relatively simple to achieve. It is recommended that a hot water tank jacket should be at least 80mm thick. They are widely available, with an off the shelf solution available for most. Pipe lagging comes in the form of foam tube formed to clamp around the pipes or material wrapping. The most important consideration when buying is the size and shape of your tanks and pipework. Should these be inaccessible, although this is rarely the case, you may require professional help.


Home Insulation

In general terms, insulation measures for your home will be more expensive than the above and require professional assistance (with the possible exception of loft insulation). They will, however, deliver comparatively greater energy savings/carbon footprint reductions and easily return the investment required.


Wall Insulation

It is estimated that most of the heat (a third or more) of all the heat lost in an uninsulated home escapes through the walls. In general, houses built from the 1990s onwards will have wall insulation to keep the heat in, but if your house is older than that, it may not have any wall insulation at all. Houses in the UK mostly have either solid walls or cavity walls. If your house was built after 1920 it is likely to have cavity walls. A cavity wall is made up of two walls with a gap in between, with the outer layer usually made of brick, and the inner layer of brick or concrete block. The brick pattern on a cavity wall will for the most part be regular with the long faces only outwards. Pre-1920 houses are more likely to have solid walls. A solid wall has no cavity and is usually made of brick or stone. The brick pattern on solid walls will be less regular with bricks laid with a mixture of the long faces and short faces outwards. If the brickwork has been covered, you can usually tell by measuring the width of the wall. If a brick wall is thicker than 260mm it is probably a cavity wall. Whilst real stone walls (not cladding) may be thicker than this they will most likely be solid. Some houses have a different type of wall structure altogether, such as steel framed, timber framed or prefabricated concrete. In this case we would advise asking a specialist insulation installer to advise you.


Many cavity walls can be insulated by injecting insulation material into the cavity from the outside. The process involves drilling a survey hole to decide on the suitability of insulating materials, drilling holes in the outside walls, injecting the chosen insulation through the holes and then sealing them with cement. The insulation material is usually mineral wool or polystyrene beads, but polyurethane foam may sometimes be recommended in more challenging cases. Specialist equipment is required, and you will almost certainly need to employ a registered installer who should be able to complete an average house with easily accessible walls in a few hours. The work should be hardly visible on completion. If you have any damp patches on your internal walls they should not be insulated until the problem is resolved.

Solid walls can be insulated either from the inside or the outside. Whilst typically costing more than insulating a standard cavity wall the savings on your heating bills will be bigger too. In both cases it can reduce costs if you plan insulation to take place with other home improvements as internal insulation will require room redecoration and external insulation will most likely require scaffolding. Internal insulation is achieved by fitting rigid insulation boards to the wall, or by building a stud wall filled in with insulation material such as mineral wool fibre. Clearly this can be quite disruptive as will require the removal and re attachment of skirting boards, doorframes and external fittings. It will also slightly reduce room size (typical insulation thickness being 100mm). External insulation is less disruptive and will not reduce room size, but is likely to be more expensive and will change the appearance of your external walls. It is achieved by adding an insulation layer to the outside of your home covered with a decorative layer of render or cladding. For a high-quality installation and finish, multiple layers will be involved to create a flat surface to affix the insulation and a prepared surface to affix the final finish. A wide price range and choice is available and safety standards and aesthetics will clearly make up a large part of the choice. Again, we would recommend employing an expert to advise on and carry out this work, especially as damp problems can be caused by solid wall insulation.


Roof Insulation

Next look to your roof where it is estimated a quarter, or more, of heat loss in an uninsulated home occurs. All roof types can be insulated but if you use your roof space as a heated room you need to insulate it and ventilate it as you would any other room using the “solid wall” internal insulation approach.


For a pitched roof, if your loft is easy to access and has no damp or condensation problems, it should be possible to insulate yourself, using rolls of mineral wool insulation. The first layer should be laid between the joists (the horizontal beams that make up the floor of the loft), then another layer at right angles to cover the joists and make the insulation up to the required depth (400mm). Make sure to walk only on the joists and support your weight with a board laid across the joists whilst working. If you use or plan to use the loft or attic for storage, you will need to have boards over the joists. Unfortunately, in nearly all cases, if you only insulate between the joists the insulation won’t be thick enough. You can, however, raise the level of the floor by fitting timber battens across the joists, or purpose-built plastic legs that fit on the joists and support the new floor. Make sure to leave a small air gap between the insulation and the boards to prevent condensation on the underside of the boards. An alternative way to insulate your loft is to fit the insulation between and over the rafters (the sloping timbers that make up the roof itself). This is achieved using rigid insulation boards, carefully cut to size, or having foam insulation sprayed between the rafters. Whichever approach you use, you will need a specialist professional. In addition, you will need to insulate any gable walls, party walls and chimneys in your loft for this approach to be effective. It will be considerably more expensive but would allow you to board your loft without raising the floor and create a warmer loft space where any tanks or pipes would be unlikely to freeze. Again, you would need to make sure your roof is in good condition and damp problems are solved prior to insulating. If your loft is hard to access, you can have blown insulation (mineral wool fibre, treated cellulose or polyurethane foam) using specialist equipment.

A flat roof should preferably be insulated from above as insulation underneath will often cause condensation problems. A layer of rigid insulation board can be added either on top of the roof’s weatherproof layer or directly on top of the timber roof surface, with a new weatherproof layer on top of the insulation. Building regulations now require this to happen on any replacement flat roof.


Ground Floor Insulation

Finally Insulating your ground floor, whilst estimated at less than 25% of heat loss from a non-insulated home, will contribute to reducing energy bills/carbon footprint and is a must if you want to install underfloor heating. Payback can be up to ten years but could also increase your EPC rating thereby increasing the saleability of your property. Insulating upper floors is generally not worthwhile unless they are above unheated spaces such as garages, workshops etc. Most homes, especially newer ones, will have a ground floor made of solid concrete. Some older homes have suspended timber floors normally indicated by air bricks or ventilation bricks on the outside wall(s) of your house that are below floor level. If you have a basement or cellar beneath your house that you can get into safely, take a look to see what type of floor you have. If the floor is a suspended wooden floor, you will probably be able to see wooden joists and the undersides of the floorboards. If you don’t have access to the space underneath your house, you will need to lift a corner of the carpet and underlay to have a look.


Solid floors are insulated using rigid insulation foam, which can be fitted either above or below the concrete. Make sure that if you need to replace a concrete floor, your builder puts in insulation as it is now required to comply with building regulations. Insulation below the concrete should allow heat absorbed by the floor to be retained for longer, however, insulation laid above the concrete will assure more rapid room heating. You can still insulate your solid floor without replacing it. Rigid insulation can be laid on top of the original floor and flooring laid over it. If you are installing underfloor heating a screed will also be used to fix the piping and level the floor. This will raise the level of the floor, so you will need to trim doors are trimmed shorter and refit skirting boards to the new level. Electric sockets may also need to be moved.


Timber floors can be insulated from underneath if you have a cellar, or by lifting the floorboards if not, and laying mineral wool insulation supported by netting between the supporting joists. A recent innovation is the use of robots to spray insulation onto the underside of the floorboards from the confined space beneath them. This clearly avoids the need to lift the floorboards but will typically cost more. Unless you have an accessible floor underside from a cellar or are comfortable pulling up and relaying floor boards professional help is a must. Also, be sure that at the end of the process any flooring gaps or skirting board gaps are filled.

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