How to draught-proof your windows
Draught-proof your windows to save on energy bills using our advice on weatherstripping, window film and how to seal gaps
Now that we’re all keeping a watchful eye on our energy bills, it’s important to keep our homes as warm and toasty as possible. And since 10-25% of heat loss in homes is through the windows, learning how to draught-proof a window is an important skill to have. Luckily, there are a number of simple steps you can take to remedy the problem, no matter what type of windows you have.
And for just click here for advice on preventing draughts around doors, too.
What is a draught?
A draught is defined as a current of cool air in a room or other confined space.
How to draught-proof windows
First, remember that it is important not to compromise ventilation routes, so never block window trickle vents. And make sure you avoid over draught-proofing windows in kitchens and bathrooms where the moist air needs to escape, or else you’ll end up with mould and damp issues.
There is also one other point to remember when undertaking any kind of sealing or draught-proofing in a room – if you have any kind of gas appliance in your home e.g. gas cooker, gas fire, gas boiler, these appliances need a consistent supply of fresh air in order to burn safely. If they don’t have this, then they won’t operate correctly and will produce a build-up of carbon monoxide which can be fatal!
Before you head to the DIY store to buy draught excluder supplies, you need to understand what type of windows you have. The way a window opens will be a deciding factor in the best way to draught-proof it. Casement designs are common and tend to be side hung and swing open in a similar way to a door.
Sash windows are more often found in period properties and have two panels that slide up and down. Other styles often found in more modern properties include sliding, tilt-and-turn and bay designs. In some windows the glass is fixed and is not designed to be opened.
To check if your windows have a draught coming through, there are some common telltale signs to look out for. These include cracked window panes, a cracked or damaged seal or condensation on the windows or between the panes of glass. If you do spot any of these signs, don’t worry, because one budget-friendly hack you can try is to use clear nail polish to paint over the cracked seal. You might need to paint on two to three coats to ensure the crack is fully covered.
For most windows that open, buying draught-proofing strips to stick around the window frame and fill the gap between the window and the frame is the quickest and simplest solution to prevent draughts. There are two main types:
• Self-adhesive foam strips, which are cheap and easy to install, but may not last long. These can also be used as a door draught excluder.
• Metal or plastic strips with brushes or wipers attached, which are long-lasting, but cost a little more.
Make sure the strip is the right size to fill the gap in your window. If the strip is too big, it will get crushed and you may not be able to close the window properly. If it’s too small, there will still be a gap for draughts to whistle through.
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You will need:
- Soapy water
- Lint-free cloth
- Measuring tape
- Self-adhesive weatherstripping
• The strip should be fitted on the inside of the window frame and needs to be tightly compressed when the window is closed. The strips come in a variety of thicknesses and you should choose the thickest option that still allows your window to close tightly.
• If you’re re-installing weatherstripping, remove the old strips and any leftover adhesive with oil or a specific adhesive remover. Clean around the window frame with mild soap and water to remove any grease that might prevent the new weatherstrip from sticking. Thoroughly dry any surface you’ve cleaned before applying the new strip.
• Measure the length of one side of the window frame and cut the weatherstrip to size, preferably in one length. It’s better to cut it a little too long and trim down afterwards, because you want to get it right into the corners. Peel away the backing and press the weatherstrip into place. Repeat around all sides of the window frame.
For sliding sash windows, foam strips do not work quite so well. Read on to find out how to stop draughts from sash windows...
How to apply window film
If your single-glazed windows are cold and draughty, then window film is an easy and affordable way of adding another layer of insulation. It acts like double-glazing without the hefty cost of replacing your existing windows. For the best results, use specifically-designed thermal film. You can buy kits with thin plastic film for very little money.
If you’re using a kit, follow the manufacturer’s instructions to stick the film to your window. The application method depends on the type of window insulation kit you're using and the specific material or style of film. While instructions may vary per product, here are some basic steps to take when applying insulation film:
You will need:
- Measuring tape
- Soapy water in a spray bottle
- Window squeegee
- Methylated or white spirit
- Lint-free cloth
- Window film
- If you’re using static cling film, unroll the film and cut it down into pieces to fit the glass portion of your windows. Cut the film approximately 2.5cm longer and wider than each window's actual size.
- Thoroughly clean your windows with a solution of warm water and soap. The glass should be wet for application.
- Remove the film backing and use your hands to apply the static cling film to the glass. Smooth out any air bubbles, and use the application tool included with the kit to squeegee out any remaining water or bubbles. If a tool isn't included, you can use an old credit card.
- If you’re using adhesive-backed film, unroll the adhesive window film, making sure that the adhesive side is facing up. Cut it down into pieces that match your window size, leaving each piece 2.5cm wider and longer than the actual window size.
- Use the included solution to clean and wet down your windows. If a solution isn't included, you can use a mixture of water and mild soap or baby shampoo. Make sure to leave the windows wet for application.
- Apply the film evenly to each window, using your hands to smooth out large bubbles. Use the included tool or an old credit card to remove smaller bubbles and excess water.
- Once the film adheres to the window, use a hairdryer (if directed) to apply heat to the film. In most cases, the dryer should only be used for 60 seconds or so.
How to draught-proof sash windows
Often found in period properties, sash window can provide a home with a oodles of character but, like many areas of your home, they do require maintenance. Common issues if this is ignored can include cracked putty, failure of joints, wet rot, rattling or sticking and draughts. Poorly maintained sash windows can cause draughts within a room that can be the equivalent to a small open window, making your living space uncomfortable to be in and also wasting you money on your heating bills.
Sealing a sash window to stop draughts is tricky as they tend to rip off any glued-on window seals when the window halves are slid up and down. The gaps also tend to be irregular over the length of the channels of the frame so that sometimes several layers of traditional sticky seals need to be applied which can lead to even bigger problems with peeling. However, there are several ways you can draught-proof sash windows yourself. The main DIY-friendly window draught stoppers for sashes are as follows:
If you're happy having your window fixed shut because it’s rarely, or possibly never, used then it would be advisable to seal the window closed with silicone. Silicone sealant is readily available and easy to apply using a caulk gun, but once it’s in place, it’s not so easy to remove. If the window is needed as a fire escape this is not a viable option. To understand more about sealants, caulks and adhesives, click here.
You will need:
- Utility knife
- Soapy watey
- Caulk gun
- Masking tape
- Methylated spirit
- Lint-free cloth
- Foam backer
- Smoothing tool
- Silicone sealant
• Choose a flexible silicone sealant that’s specially designed for outdoor use to withstand weather and temperature changes.
• Carefully remove any old sealant using a utility knife. You can cover the window frame with masking tape if you’re worried about scuffs. Clean around the frame with mild soap and water to remove any dirt or grease that would prevent the sealant sticking. Dry the surface. Use a lint-free cloth to wipe the area with methylated spirits if any residue remains, then allow to dry.
• If the gap is fairly deep, push foam backer into it with a scraper. Use masking tape to tape off the frame and wall a few millimetres either side of the gap. This will help you get a crisp, clean line.
• Squeeze the trigger of the caulk gun steadily as you move along the gap, wipe off any excess with a smoothing tool or a wet finger. Remove the tape before it dries.
Although not always that effective long term, because as you use your windows the movement will dislodge the draught seals, these certainly are cheap and very easy to install.
Self-adhesive brush seal or metal weatherstrips
These come in many different guises and are commonly sold in two parts, with a self-adhesive 'pile carrier' – rebated plastic or metal strips – designed to be stuck around the window frame into which the fluffy brush or pile strips are slotted to stop draughts. Although these do prevent draughts, bear in mind that they may need replacing over time depending on how often you open and close your windows.
Temporary window sealer
These products are designed to seal up sash windows during the colder months before being removed again when the weather warms up and you want to open the window. One such product is Gapseal, a flexible, non-permanent window sealer, which comes ready to fit into window gaps between 2mm-7mm and with all the tools you need to secure it into place.
Once fitted, it expands to fill the entire gap yet can be taken out when no longer needed. It can be used many times, doesn’t absorb moisture and will bridge most gaps.
Although some feel that fitting secondary glazing will ruin the aesthetic of a sash window, and in the past this was true, today there are quite a few specialist companies that supply bespoke secondary glazing units that are designed to blend in with your existing windows and be as unobtrusive as possible.
Secondary glazing involves essentially adding another window to the inside of an existing one – and is a job probably best left to a professional. A secondary window is fitted behind your existing sash window, as near or far to the existing window as you require. This secondary window, once closed, then seals the existing sash window in front of it preventing any draughts from passing into your room. They come in a variety of different designs that include upward and downward slide opening, inward opening and they can even be removable enabling you to fit them in the winter when you will be less likely to want to open them and then remove them in the summer when it’s warmer. They can also be purchased as glass or lightweight Perspex.
How to draught-proof uPVC windows
Draughts in uPVC windows are most commonly caused by gaps forming around them. This can be caused by damage, dirt or the windows dropping and causing misalignment. To find the gaps in your window, simply run your hand over your window during a windy day, wherever you feel a draught coming from will be where your gap is. In rare occurrences, a draught will be coming from a crack or damage within the glass of your window, if this is the case it will be visually obvious, and you should always get the window replaced as soon as possible.
Luckily, there are a number of solutions to prevent draughts in uPVC windows that don’t need you to resort to replacing the entire window unit:
For most draughts in uPVC windows, weatherstripping is usually the solution stop the wind whistling through the gaps between the window and the frame. However, sometimes other factors can cause the draughts.
Check window seals
Draughty uPVC windows need effective seals. There are two rubber seals on each opening window. It might be that both have perished or it could be just one of them - feel if the rubber is still flexible by pressing it with your finger. If it feels hard then it’s likely that it’s perished and will be unable to compress properly when the window is closed, allowing cold air to seep through.
Another common cause of draughts with window seals is shrinkage. Quite often you can see the rubber has shrunk at the comers of the frame leaving a gap where the cold air creeps in. In both instances it’s best to replace the seals, which is a fairly inexpensive job to do.
Occasionally, a window can become draughty because the hinges are dirty or rusty. It’s good practice to give the hinges a thorough clean at least once a year to avoid them becoming unaligned and leaving gaps. If you’ve removed any dirt build-up and you’re still experiencing draughts, it could be a sign of further damage to the hardware. You can pinpoint problems with the hinges by closing the window and checking for gaps between the window and the frame. If there is a gap, it means your hinges are damaged or faulty and you should either get the hinges, or if necessary, the entire window replaced.
Hinges need to be lubricated once a year too, if they are left unused or are in a damp area, such as a bathroom, they can seize up. If this is the case the back edge of the hinge fails to engage causing a gap when you try to close it.
If your window lock is faulty and stopping the window from closing correctly, it will not only let in draughts, but your home insurance will be void. This is one reason you should look at getting the locking system replaced or replacing the entire window unit. You can test the tightness of your lock by sliding a credit card between the sash and the frame, if you notice it moving freely then your lock needs tightening or replacing.
To prevent espagnolette locks from corroding, they need lubrication annually to prevent the locking strip from jamming. Applying excess force breaks the gearing and prevents the bolts from engaging. Once it has jammed, the locking side of the window allows air to seep through the gap. Luckily, uPVC window locks are easily replaced at a reasonable cost with a minimum of fuss.
Draught-proofing windows with thermal curtains
If you’re not a confident DIYer, but still want to prevent draughts from creeping into your room from the windows, then add additional insulation by hanging a thick pair of curtains with a thermal lining.
If you don’t want to buy a whole new set of curtains, you can buy separate, inexpensive linings which simply clip to your existing curtains from stores such as Dunelm. For a real belt and braces approach, consider using a thermal-lined blind at your window too.
Replacing your windows
If draughts from your windows are an ongoing issue and can’t be resolved with retro-fitted draught excluding methods, you should look at replacing your entire window unit.
Although replacing the windows in your home may seem like a more expensive commitment, you’ll receive a return on investment when you sell your home and save yourself money annually through your energy bills. If you have visible damage to your window frames or glass panes, you need to have the window replaced as soon as possible. The damage will only get worse and cause further issues. Any visible damage to your windows will cause weak spots, leaving your home vulnerable to intruders.
Anna-Lisa De’Ath is a freelance magazine editor and journalist specialising in homes & interiors, gardening and crafts