The parts of a house that you should never insulate

Winter always feels like a game of chicken: seeing how long you can last before turning on the heating full-time. If this sounds like you, you’ve probably already looked at ways to improve your home’s insulation. But in your bid to save on energy bills, it’s worth noting that there are certain areas of a home that you shouldn’t insulate.

In fact, if insulation is installed incorrectly or in the wrong places, it can do more harm than good. While there are a number of places that you should definitely take into account when it comes down to it how to insulate your homethere are some that you should never isolate.

1. Near or around heaters, boilers and radiators

As you would expect, you should avoid placing the insulation too close to the wall best electric heaters or boilers, as this can cause various problems. ‘If you insulate too close to these units you risk them overheating, which can lead to equipment failure, system inefficiency or even a fire hazard. These areas require adequate ventilation to properly dissipate heat,” says Mike Storey, insulation expert at British specialists in the field of flat roofs and insulation.

It is also imperative that you keep the space around the boiler flues clear. Blocking them can disrupt ventilation and pose safety risks. Insulating around radiators and other heating methods can also “reduce their efficiency in heating rooms, as they need good airflow to circulate heat effectively,” says Gary Jarman, construction expert at Construction store.

Boiler in cupboard

(Image credit: Future/Colin Poole)

2. Around vents

Vents can often make our homes feel a little colder, especially in the fall and winter when temperatures start to drop. But “although they may feel drafty, you should never cover a vent with insulation or use draft-blocking materials to block them.” MijnJobQuote.nl‘s real estate and construction expert, Thomas Goodman, reveals.

“This includes vents chimney breastsin the roof and air stones under floating floors. Confining them prevents the movement of air, which traps moisture,” he continues. And this can lead to significant moisture problems in the long term.

A kitchen with a brick wall and copper lighting fixtures on the wall

(Image credit: Future PLC/Davit Parmiter)

3. About electrical cables and wiring

‘Attic insulation overwiring is also a tricky issue,” says Mark Glenney, founder of The Stairlift Shop. “In general, it is safe to lightly cover electrical cables, but make sure the insulation is not too tight around them,” he continues. The reason for this is that the wiring needs space to dissipate any heat and tight insulation around or over cables or wiring can increase the risk of overheating. So you’ll want to check the insulation type and make sure it meets British Standards. It is not without reason that there are guidelines on safe distances between insulation and electrical components.’ And quite a few experts agree with this sentiment.

‘Covering wiring with attic insulation is generally fine, but you do need to make sure your wiring is properly rated and that any junction boxes are properly insulated so they don’t overheat and cause a fire hazard,’ says Becky Lane, co -founder and CEO of Furbnuagrees. “If you’re in doubt, it’s always a smart move to have your wiring checked or upgraded before installing the insulation.”

Not only can it cause wires and cables to overheat, but it “can also reduce the current-carrying capacity of the cable,” confirms Paul Spence, technical manager at Is called. Essentially, “cables should only be covered with insulation if an electrical expert has confirmed that this will not unduly reduce capacity,” he claims.

Gold-painted bedroom with bed, fireplace and sofa with antique elements

(Image credit: Future PLC)

4. Cavity walls in older homes

While most cavity walls can be insulated – and that’s probably one of the most common places where insulation is added – there are a few cases where it’s better not to, experts agree. For example, did you know that older homes and properties are built with solid walls that are meant to breathe? And because these walls rely on airflow to control moisture, “improper cavity wall insulation can lead to condensation problems,” says David Miloshev, an electrician and home improvement expert at Fantastic services.

If you plan to insulate the cavity walls of an older property, you may need to use breathable insulation materials to maintain this ability.

Dining room with white radiator and wooden dining table with accessories

(Image credit: Future PLC)

5. Under floorboards in older homes

Here too, this mainly concerns older homes and Luis Montes, structural engineer, expert in the field of heavy equipment and editor-in-chief at Fortis HDproposes that the voids under the floor of ‘older houses’ should not be insulated.’ This is because ‘some older houses in Britain have floating wooden floors with air bricks around the base.’ And these air stones help ventilate the room and prevent moisture from building up. But once you insulate or block off this area, moisture can become trapped under the floor, which in the worst case scenario can lead to wood rot and even structural problems.

“This mistake has cost people expensive repairs,” Luis reveals.

6. Attic or eaves

Blocking these can also lead to condensation, damp and even mold ‘and it’s important to keep them clear so the lifespan of the roof isn’t compromised,’ warns Gary. The last thing you want is to have to do that replace your roof because you have insulated your roof edge incorrectly.

Yellow painted rendered house with red roof tiles

(Image credit: Future PLC/Darren Chung)

7. Any damp areas in your home

There is nothing more frustrating than finding damp or excess moisture and condensation in your home. But if you are considering insulating a room that is already sensitive to moisture, this is not a good idea.

“If you don’t address the moisture first, the insulation will trap it and lead to mold, mildew or rot.” And this will degrade the insulation over time and reduce its effectiveness, possibly even weakening surrounding structures,” says Mike.

So it is important to solve any moisture problems before you even think about insulating these areas of your home as this could not only make the problem worse but you could actually be wasting your time and money installing any form of insulation before it is fixed. You could have a leak or something as simple as too much condensation. Make sure you understand why this happens before you consider insulating this part of your home.

Yellow bedroom with white bedding and a silver radiator on the wall under a window

(Image credit: Future/James French)

Frequently asked questions

Can too much insulation cause moisture?

“It’s not that you can have too much insulation, but that you can have too little ventilation,” Thomas explains. Essentially, the wrong type of insulation can also cause damp. For example, using non-permeable insulation under a wooden floor blocks airflow, leading to a build-up of moisture that can potentially rot beams and floorboards. Likewise, older homes are built with sturdy walls designed to breathe. So you may need to use breathable insulation materials to maintain this ability,” Thomas adds.

It’s also important that your walls are in good condition before insulating them, otherwise you could make damp problems worse. For example, if you apply mineral wool insulation to the inside of your walls before fixing existing damp problems, there is a good chance that it will sag and lose its insulating properties. Moreover, it will grow mold and your walls will become wet.

Which parts of your home need insulation?

While we have outlined some places that should not be isolated, there are some that can make a big difference in a positive way. The most obvious room is your roof or attic. According to the experts, this is because about 25% of the heat from the house is lost through the roof. “It’s also one of the easiest and cheapest places to add insulation,” Thomas argues. ‘Blanket insulation costs around £25 and can be fitted yourself if you are on a budget. Or if you have a vaulted roof, you need to add insulation between the trusses.” Don’t forget to leave some space for ventilation.

And considering that this can save you hundreds of euros on your energy bill, this is something to seriously consider. Another area you may want to pay attention to is your pipes and hot water tanks. By insulating them you help the entire heating system retain its heat, allowing them to work more efficiently and preventing heat loss. save your money on your invoices.

So there are quite a few things to consider before you start insulating your home, whether that’s through a DIY project or by consulting a professional.