Bathrooms are one room in the house that really need to offer a consistently comfortable environment – after all, you are likely to spend much of your time in this space in a state of partial or total undress. Not the place for sub-zero temperatures.
You might think you are doing all the right things – installing one of the best bathroom extractor fans, fitting correctly sized heated towel rails and radiators or even an underfloor heating system – yet if you are still finding yourself shivering when you step out of the shower, something is not right.
It might surprise you to learn that your extractor fan could be the culprit here – we spoke to the experts to explain why this might be and how to put a stop to this icy issue once and for all.
Can bathroom extractor fans make a room feel colder?
Many people have never considered that their extractor fan might be interfering with their bathroom heating, causing their room to feel chilly yet, according to the experts, this is a far more common problem than you might think.
"Extractor fans play an important role in controlling moisture, but if they're not correctly specified or set up then they can make a much bigger impact on heat loss than homeowners may realise," explains Ryan Marshall, director of Marshall Clean Heat and Power. "Bathrooms are usually small, highly heated spaces, so even a modest extraction rate can replace warm air with cold air very quickly – especially in colder months."
Martyn Fowler, founder of Elite Renewables, elaborates. "The fan changes how air behaves in a controlled space. When an extractor fan runs, it creates negative pressure in the bathroom. That means air has to come from somewhere to replace what’s being pulled out.
"If the door is open, it might pull warm air from the rest of the house," continues Martyn. "If the door is closed and the room is sealed, it can draw in colder air through gaps in the building envelope, such as trickle vents or even the fan duct itself if there’s no backdraught damper."
There are actually several reasons why bathroom extractor fans might end up causing more problems than they solve – we're here to reveal them.
Ryan Marshall is managing director of Marshall Clean Heat and Power, a UK-based specialist in renewable heating and energy solutions. A time-served heating engineer with an MBA and Chartered Manager status, Ryan founded the business in 2008 and has since led its growth with a strong focus on clean heat technologies, energy efficiency and practical decarbonisation. He is passionate about helping homes and businesses transition to low-carbon energy with confidence.
Founder of Elite Renewables, Martyn Fowler is one of the UK's leading renewable technology experts, working with heat pumps for the last two decades. His passion for decarbonisation matched with a deep technical experience of the technology make him one of the industry's go-to experts for all things renewable.
1. Fans that are left to run for too long
Bathrooms can become steamy places meaning the temptation can be to leave your extractor fan running at full blast long after it has been used in order to dispose of all that damp, hot, muggy air – but this could be a big mistake.
"One of the most common issues we see is fans running for longer than necessary," reveals Ryan Marshall. "Long overrun times or continuous-run models can remove more warm air than your heating system can comfortably replace, which leaves the room feeling noticeably colder."
"The most common issue is fans that run constantly or stay on far longer than they need to," agrees Michael Zohouri, founder of Pyramid Eco. "If the fan keeps pulling air out after the moisture has cleared, you’re just removing warm air and replacing it with cold from other parts of the house."
The solution: "Start by checking how the fan is controlled," says Michael. "If it’s wired to the light switch, think about upgrading to a humidity-sensing model. These only run when moisture levels are high and switch off when things are dry again. So you don’t lose any heat just because someone forgot to turn it off."
Michael Zohouri is the company founder, bringing over a decade of experience to the role. His expertise spans energy-efficient retrofitting projects, including insulation, solar and heat pump installations. Committed to addressing challenges like thermal bridging and improving air quality, Michael focuses on creating healthier, more sustainable living environments while reducing energy costs for residents.
2. Faulty or missing backdraught damper
All extractor fans used for bathroom ventilation should be fitted with a backdraught shutter, a valve that opens when the fan is running to let stale air out but that should then automatically close when the fan is not in use.
"It’s really important that the fan has a proper backdraught shutter that seals fully when the fan is off," explains Martyn Fowler. "Without that, the duct can act as a pathway for cold air to move back into the bathroom."
"If the fan hasn’t got a working backdraught damper, or if the ducting around it isn’t sealed properly, cold air can come back in from outside," adds Michael Zohouri. "Sometimes you’ll actually feel the chill coming straight through the fan."
The solution: Take a look and check that the backdraught flap is working and sealing properly when the fan is off.
"Insulated ductwork and a good-quality non‑return valve will make a big difference by preventing cold air being pulled or blown back into the bathroom when the fan isn’t operating," says Ryan Marshall.
3. Choosing a fan that's too powerful
Choosing an extractor fan that is not specified correctly for the size of you bathroom can cause all kinds of problems, heat loss included – if it is not powerful enough it won't pull the stale air and steam out properly, but if it is too powerful you could find yourself wasting both heat and energy.
"One of the most common issues is excessive air extraction – if a fan is too powerful for the room size, it can pull warm air out faster than it’s replaced, creating a noticeable chill," explains Ruth MacEachern, product manager at ventilation specialists EnviroVent.
"Bigger isn’t always better," agrees Michael Zohouri. "If the fan is rated for a much larger room it will pull out too much air too quickly and take the heat along with the steam."
The solution: Choose an extractor fan with the correct extraction rate for your bathroom's size. Calculate its volume by multiplying it length by its width by its height (L x W x H). It is advisable to have at least four air changes per hour so you would then multiply the figure you got by four. This would give you the required extraction rate of your fan in m3/h.
Ruth MacEachern is product manager at EnviroVent, one of the UK’s leading manufacturers and installers of sustainable, low-energy domestic ventilation systems.
Shop our favourite bathroom extractor fans
This well-priced extractor fan ticks so many boxes – quiet to run (27dB) and easy to install, it also has a backdraught shutter and overrun timer. It is suitable for a standard 100mm duct.
This extractor fan is super quiet to run (14dba) features two speed settings and has an adjustable overrun timer – plus, backdraught shutters are included. It also looks pretty smart.
While not as quiet as the others here (30dBA), this extractor fan features a humidistat to set between 60-90% and an overrun timer meaning it won't be running for longer than needed.
4. Bad extractor fan positioning
It is no good just sticking your extractor fan in any old position within your bathroom layout – while you might not want it ruining your bathroom design ideas, you really need to give some thought to its location if you don't want it to be the cause of post-bath shivering.
"Layout matters," states Martyn Fowler. "If the extractor is positioned directly above the shower or bath and runs for long periods, it can strip warm air very quickly and cause a noticeable drop in temperature."
The solution: "In compact bathrooms, drawing air from a higher corner or slightly away from the shower can still remove moisture effectively, but in a more controlled way," advises Martyn.
5. Speed settings are being overlooked
Running your extractor fan flat out in a quest to beat mould in the bathroom is not the best method of getting the most out of it – just another way in which it could make your bathroom feel cold.
"Fan speed plays a key role," says Martyn Fowler. "Many newer models offer variable speed settings, which makes a big difference in smaller bathrooms. Instead of running flat out all the time, the fan can operate at a lower rate for background ventilation and only ramp up when steam levels rise. That reduces how much warm air is removed and helps keep the room temperature more stable."
The solution: Choose an extractor fan with variable speeds and that responds to the moisture levels in your space.
"A humidity-controlled fan works on demand," explains Martyn Fowler. "It switches on when moisture levels rise, and switches off once the air has dried out. That means you’re removing steam when it’s needed, but you’re not continuously pulling warm air out of the room once the job is done."
6. Uninsulated fan ducting
It is crucial, if you want to maintain a comfortable temperature in your bathroom, that you check the way your extractor fan is ducted to outside. It is also really important to ensure that the ducting you use is insulated.
"Poorly sealed ducting or gaps around the fan housing can allow cold air to enter from outside," explains Ruth MacEachern.
The solution: "Make sure your ducting runs properly to an outside wall or roof vent, and that it’s insulated if it goes through a cold loft," advises Michael Zohouri. "That stops condensation forming in the duct and helps prevent cold air from being pulled in."
7. Drawing fresh air from a cold spot
Along with checking that ducting seals are intact and that insulation has been considered, do think about how the source of your fresh air could be affecting bathroom temperatures.
"When a fan pulls humid air out, it has to be replaced from somewhere else in the property," picks up Ryan Marshall. "If that 'make-up' air is being drawn from unheated areas, such as hallways, loft voids or through draught points, the temperature drop can be significant, especially in older or less airtight homes."
The solution: Along with making sure your fresh air is not coming from an unheated area, and addressing draught proofing throughout your home, Michael Zohouri has another solution.
"Keep the door closed when the fan is running," he says. "This allows the fan to draw air from under the door rather than from the rest of the house."
FAQs
Do bathrooms need extractor fans?
If you are renovating a bathroom that currently has no extractor fan, you may well be keen to avoid any extra disruption – but is an extractor fan a legal requirement?
The UK Building Regulations state that bathrooms must have some form of ventilation, although this can be provided in the form of either an extractor fan or an openable window. However, in the case of new builds, bathrooms are required to be fitted with mechanical ventilation (due to them being more airtight).
Even if you are not building a new house, it is still highly recommended to fit an extractor fan. Opening a window for prolonged periods in the depths of winter to deal with humid, stale air is impractical, plus mechanical ventilation is a great way to avoid issues with damp or mould arising.
If you have found damp in the bathroom you should not only address your ventilation methods, but also be on the lookout for leaks in pipework or behind tiles. If you can, opening windows for a few minutes every day will help too.
