In theory, a porch should work like an airlock. You step in, shut the outer door, then open the inner one, and the warm air in your hallway stays where it is.
In practice, plenty of porches leak and let the warmth out of your home. Instead of holding heat in, they give it an easy way out, and your boiler has to work harder to replace it.
Whether you already have a porch or you're still weighing up porch ideas for your entrance, the weak spots tend to be the same. Here are the seven things experts say to look out for, and how to fix them.
1. A badly fitted internal door
"The inner door is particularly important because it separates the porch from the heated part of the house," explains Nick Duggan, managing director of The Radiator Centre. "If the porch itself is cold, a well-fitted door with good seals helps stop that chill spreading into the hallway, reducing the need to turn up the heating elsewhere."
Luke Burford, co-founder of Compare Builders, agrees this is the place to begin: "If the porch is unheated, start by checking the door into the house: that's what separates your warm living space from the cold porch."
A door that rattles when it's shut, a latch that needs a shove, or daylight around the edges are all signs it isn't sealing properly. Tightening loose hinge screws and moving the strike plate slightly so the door pulls tight against its stop will often solve this. If the door catches rather than gapes, find out why doors stick in their frames before you reach for the planer.
Mark Irving, building expert at Build & Plumb, says the inner door should also "have a draught excluder so that warm air does not escape." It's the same barrier that stops a draughty porch making your hallway feel cold, so the fix pays off twice.
This weatherstripping tape is made of environmental friendly woven material, is super adhesive, durable and waterproof. It's perfect for sealing internal doors and keeping your house warm in winter.
Nick has over 20 years of experience in central heating and radiators, leading the team at one of the UK's largest independent suppliers.
Luke Burford is co-founder of Compare Builders, which matches homeowners across England and Wales with vetted builders for projects ranging from porches and extensions to full renovations.
Mark has over 20 years of experience in the building sector, leading to a wealth of knowledge surrounding building and renovating that he enjoys sharing with others who are looking to complete their own building projects.
2. A poorly sealed external door
Even if your porch is unheated, a sealed outer door is essential. The tighter it is, the warmer the buffer of air inside the porch, and the less heat your hallway gives up each time the inner door opens. If the porch is heated, or the original front door has been taken out, it's the only thing standing between your heating and the outdoors.
"It's worth checking the letterbox and keyhole, particularly on older doors, which can allow cold air through even when the door itself fits reasonably well," says Scott Godfrey, construction trade consultant at Black Hammer.
The rubber compression seals in the frame are the next thing to check. Flattened or cracked ones are cheap to swap, and there are plenty of other simple ways of draught-proofing a front door without replacing it. If the door itself is warped or past its best, a modern insulated design will do more than any seal, and these front door ideas show what's out there.
Scott Godfrey is a master craftsman and carpenter with over 20 years of experience in carpentry, joinery, and both bespoke and large-scale construction projects.
3. Gaps beneath the door
"Even small gaps can let cold air in, so replacing worn seals and fitting a suitable draught excluder can make a noticeable difference," says Nick Duggan.
A gap at floor level is often the biggest single leak in a porch. Whenever warm air escapes from the house, cold air is pulled in to take its place, and the space under a door is the easiest route. To check yours, close the door on a sheet of paper laid across the threshold. If it slides out easily, the seal isn't doing its job.
On internal doors, a screw-on brush strip copes better with uneven floors and is one of the cheapest forms of draught-proofing you can buy. A weighted fabric excluder will do the job while you sort out something permanent.
Shop quick fixes for gaps under doors
This robust draught excluder is built to last and is ideal for sealing gaps up to 25mm.
This weighted draft stopper is designed to fit most doorways and features handy loops for hanging when not in use.
4. Gaps around the frame and walls
"If you've got gaps between the door frame and the surrounding wall, those may need filling with an appropriate sealant," says Scott Godfrey.
Over time, the mastic where frames meet the brickwork shrinks, cracks and comes away, often behind trim where you won't spot it. Cut the old sealant out before applying new so it bonds properly, and use a flexible, exterior-grade product outside. Foam weatherstrip tape will tighten up any opening windows in the porch, too.
Don't seal everything shut
"Seal unintended gaps, but keep necessary ventilation and drainage openings clear," warns Luke Burford. That means leaving trickle vents and the drainage slots in window frames alone.
"I'd also check for signs of condensation before sealing everything up, because if you reduce ventilation without addressing moisture you're likely going to run into some damp and mould issues," says Scott Godfrey. If the porch glass is already wet most mornings, tackle the causes of persistent window condensation before you draught-proof.
5. Single glazing
"Glass has low thermal resistance, allowing warmth to radiate outwards quickly, especially when it is colder at night," says Mark Irving. How much that matters depends on how you use the porch. If it's an unheated buffer with a well-sealed inner door, single glazing is less of a worry. If the porch is heated or open to the hallway, it's one of the biggest leaks in the house.
There's some reassurance if you're thinking about resale. "An unheated porch that's properly separated from the house isn't normally included in the heated floor area for EPC purposes, so single glazing in the porch won't automatically drag down the rating," says Robin Edwards, buying agent at Curetons Property Finders.
If you do want to upgrade, there are three routes, from cheapest to most expensive:
- Thermal window film: A shrink-on plastic film that traps a layer of air. It's cheap and removable, but best treated as a stopgap. This tesamoll Thermo Cover Window Insulating Film from Amazon has thousands of positive reviews and is an affordable quick fix.
- Secondary glazing: A second pane fitted inside the existing window. Magnetic DIY kits are affordable, and made-to-measure units suit period homes where replacing the windows isn't an option.
- Replacement double glazing: The most effective fix, but the most expensive. It's worth it if the frames are rotten anyway.
6. A poorly designed connection between porch and house
"The connection to the house needs a proper look too," says Luke Burford. "Failed seals can let air through, while missing insulation at the roof, wall or floor junction can leave cold patches even when there's no obvious draught. Those need different repairs."
Porches built over concrete slabs or unheated crawl spaces "act as a thermal sink, pulling warmth away from the room and into the ground underneath," adds Mark Irving. And Scott Godfrey points out that "lightweight porch roofs can have very little insulation."
Re-sealing the joint where the porch meets the house wall, inside and out, deals with the air leaks. Damp marks or mould along that junction usually point to the second problem: a cold bridge. Most porches can be insulated with rigid boards under the floor, inside the walls and between the ceiling joists, though larger structural work is a job for a builder. A badly detailed junction is one of several porch mistakes that are far cheaper to avoid at build stage than to fix later.
Has your original front door been removed?
"If the original front door has been removed, the whole porch needs assessing as part of the heated house," says Luke Burford. "You could be losing heat through its roof, walls and floor as well as the glass."
7. An open porch with no airlock
“I wouldn’t recommend enclosing an open porch purely to save on heating bills,” says Robin Edwards. “The cost is unlikely to be justified by the energy savings alone. In most cases, homeowners would be better off spending a few hundred pounds improving draught-proofing or upgrading an inefficient front door.”
Without a second door, an open porch can’t act as an airlock, so your front door is doing all the work. Get that right first.
If you want an enclosed porch for other reasons, such as porch storage or security, weigh up the pros and cons of enclosed vs open porches and find out what a porch costs before you commit.
“A porch is worth considering if it improves how you use your home, but probably not purely as an investment,” says Edwards. “A well-designed porch can be a lovely addition, but a poorly executed one can be an expensive mistake.”
FAQs
Which fix should you tackle first?
"Find out exactly where the cold air is entering before spending money on insulation or replacement windows, or you could end up fixing something that wasn't responsible for the problem in the first place," says Scott Godfrey.
On a cold, breezy day, run a damp hand slowly around each door and window, or use a thermal camera to show up the cold spots. Then follow Luke Burford's rule of thumb: "My order would be to sort the draughts and door fit first, then assess the glazing and insulation."
- Adjust and seal the internal door
- Seal the gap under each door, plus the letterbox and keyhole
- Replace worn door seals and re-seal the frames
- Upgrade the glazing
- Insulate and re-seal the porch structure and its connection to the house
- Only then think about bigger changes, such as enclosing an open porch
The first few jobs are cheap and can be done in an afternoon, which makes the porch one of the quickest wins when you're preparing your home for winter.
Should you just turn up the porch radiator?
"If you have a radiator in the porch, it's worth remembering that adding more heat won't solve the underlying problem if warmth is escaping through draughty doors or poorly insulated surfaces," says Nick Duggan. "Deal with these issues first, then consider whether the existing heating is adequate for the space. Otherwise, you could end up using more energy than necessary just to keep the porch comfortable."
If the radiator still struggles once the leaks are sorted, it may simply be too small for the space. Many of these hallway radiator ideas work just as well in a porch, and a thermostatic valve will stop it running flat out.
Once your porch is sealed, it’s worth looking at what else could be letting warmth slip away. These expert tips on how to keep your house warm cover everything from curtains and rugs, to bleeding radiators and boosting insulation.
