Turning up the TRVs won’t make the room warm up faster.

Most of us must have been guilty of doing this. It feels cold, we switch on the heating and want the room to get hot as soon as possible. What do we do to speed that up? Let’s increase the temperature, surely? So TRV goes to max.

Unfortunately, this is not how the thermostatic radiator valve (TRV) works. All it does it stop the flow of hot water when the preset temperature has been reached. It’s like a switch: on or off. If it’s on, it’s not going to make the room warm up faster. It’s only useful if you want the room to get warmer, not warmer faster, so you turn it up, or down if the room is too hot.

Most of us have some bad habits like this when it comes to radiators, perhaps because we don’t fully understand all their ins and outs. Here are 10 more important points you should know about your radiators.


  1. How to make the room warm up faster?
  2. Fit big radiators
  3. Avoid small pipes
  4. Don’t cover TRVs
  5. Don’t block radiators either
  6. Choosing the best radiators
  7. Fit a magnetic filter
  8. Insulate the pipes
  9. Don’t touch lockshield valves
  10. Let’s stay safe

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1. How to make the room warm up faster?

After saying that TRVs don’t make the room warm up faster, what does? Increasing the temperature of the hot water will, but not by much. And in any case, if it’s already at the maximum, usually 80 deg C, it won’t be able to increase it any higher!

So what can we do? Not much at this stage. If you’re fitting or replacing radiators, try to choose the biggest radiators you can afford.

2. Fit the biggest radiators you can

Alternatively, add an extra radiator in a room if there is space. The end result is the same: more heat is delivered to a room, so the room warms up much much faster than increasing the temperature of the heating water from the boiler.

That temperature can even be lowered without noticing any delay. Look at it this way. A small, red hot radiator will struggle to heat up a large room compared to a large radiator at a lower temperature in that same room. This is how underfloor heating works: the whole floor is heated up to warm the room, so the temperature of underfloor heating doesn’t need to go past 40 deg C.

The bonus with a lower heating water temperature is that the boiler doesn’t have to work as hard and less gas is burned to reach this lower temperature. Savings all around.

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3. Big radiators, big pipes

If you’re going ahead and fitting big radiators, don’t pipe them up using small pipes. They will take forever to heat up. Small pipes are cheaper, can turn around corners without requiring fittings and take up less space, so are more discrete. But you will regret it you find out that your big radiators are slow to heat up and then it will be a lot of disruption to change the pipes.

4. Don’t cover TRVs

Blocking the TRVs with clothing, curtains or furniture stops the TRVS from sensing the real room temperature. Either the radiator heat builds up around the TRV causing it to turn off the flow of water, or the heat never reaches it, in which case the room gets hotter and hotter. TRVs need good air circulation all around, without either being exposed to a draught.

5. Don’t block radiators either

Radiators work by warming the air flowing along its surfaces. Warm air rises so the flow of air is vertically up. This is why it’s important to leave a big gap above and below radiators to allow a good air flow. Putting furniture like bookcases and sofas in front of them reduces the air circulation so that the radiator just warms the air around it only and the rest of the room stays cooler.

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6. The best rads have the most surface area

Cast iron and designer radiators look cool and they are actually cooler than conventional panel radiators. But we’re talking about temperature here. Fancy radiators usually have less surface area to emit heat so they cannot heat up a room as efficiently. Conventional radiators have fins in the middle to increase their surface area and warm up more air.

7. Fit a magnetic filter

Dirt, or sludge, in the radiators will prevent them from heating up fully, causing cold spots at the bottom where it usually collects. Sludge also causes all sorts of issues and breakdowns with boilers. Many boiler warranties are usually void if no magnetic filter has been fitted. In fact, it’s now compulsory to fit a magnetic filter on all new boiler installations. The best location is just before the hot water returns to the boiler so all the dirt can be captured and only clean water enters the boiler.

So get a magnetic filter installed to protect your radiators and boilers from sludge.

8. Insulate heating pipes

If large radiators have been fitted and the heating water temperature reduced as a result, ensure that any pipes going through non-heated areas are insulated otherwise they will lose a lot of heat and the water reaching the radiators will be even cooler.

This is often the case in houses with a suspended timber ground floor – heating pipes are run underneath where it can get quite cold.

There’s also the danger of those pipes freezing in winter. While the heat of the house itself keep those pipes at a higher temperature than outside, there may be occasions when the house remains unheated for long periods. It may be a rented property, in between tenants, or the occupiers may have gone on holiday.

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9. Lockshield valves

There are two valves fitted to each radiator, one at each end. One is the TRV which is set according to the desired temperature. The other is the lockshield valve and the new ones have a smooth cap. This is to prevent people from altering them. The purpose of the lockshield valve is to regulate the maximum flow of water through each radiator so that one radiator, usually the one closest to the boiler, doesn’t take all the hot water, leaving the one furthest with little and cooler. Lockshield valves are used to balance the heating system. So if yours have been balanced, don’t touch them!

10. Safety first

Big rads are great in many ways: they warm up a room quickly and require a lower temperature. People are less likely to get burnt touching it, the boiler doesn’t have to work as hard and less gas is used. But it does come at a price, well, maybe two or three, since the first one is the cost itself and the second is the amount of space required. The third one is the weight.

Their bigger size means they’re not only heavier when empty but they can hold more water due to their size so they get even heavier when full. They require a strong wall to hold them. Plasterboard is not strong enough to hold them even if they seem to hold up at first. Over time the screws will work loose through the plasterboard and this will happen sooner rather than later. If the radiator needs to be hung onto a stud wall, the radiator brackets need to be screwed to the studs or battens added to provide a secure anchoring point.

It may be a good idea to look behind the radiators once in a while to check whether the brackets have become loose or not. Give the rad a firm tug to see if it moves. Screws into wood will not work loose but screws in a brick wall may become loose if they don’t go deep enough in the brick.

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