There’s been a lot of discussion around air source heat pumps recently, especially with the UK government’s push to using this technology.
The main reason for the push towards heat pumps is that they actually put out more energy than they use, which feels a little like witchcraft but is only some clever science. There are two heat pump types – air and ground. They’re both the same principle, but one takes energy form the air and one from the ground. The latter needs a lot of garden space and substantial drilling down into it, in some cases up to 200m deep!
Without getting too technical, the system essentially is like a fridge running in reverse. The heat pump uses a refrigerant fluid to collect the heat in the external air, collecting it into a usable temperature and transferring it indoors, either through water or air.
This system runs at a lower temperature than your traditional central heating, meaning you’ll need larger radiators and a good level of insulation. The best implementation is actually combining under floor heating with a well insulated building.
The majority of Britain’s existing buildings are drastically under insulated to heat pumps are likely to leave people feeling cold in winter. There’s also the external heat pump unit which needs to be installed somewhere, in a small terraced house this can cause some issues, and may even need planning.
Heat pumps are a great solution for new builds where the level of insulation can be sufficient and the heating system designed to make the most of the technology.
An alternative would be to use electric heaters instead of a gas powered central heating system. Traditionally, gas has always been cheaper than electric which is why as a nation we’ve relied on gas boilers for our heating. However with increases in gas prices it may start to become a viable option.
Electrical heating is a lot easier to install, there’s no gas, no water, just cables. They also allow much more control over what room get heat and when. For instance, if a a living room isn’t used in the morning then the heater in that room can be programmed to not come on until the evening. Modern electric radiators also have clever technology that vary their output depending on the current and desired temperature. So if the room is only 2 degrees cooler than the target temperature, the heater will come on at a lower level to avoid overheating.
The main issue is that electricity is still a more expensive way to heat a property than gas, although with the right supplier it can be completely carbon neutral.
Most electric heaters work on convection, like a traditional radiator – it heats up the air which rises, and is replaced with cooler air that is then heated. This means for you to feel the benefits you’ll need to heat the entire volume of the room. If you have a large room with a high ceiling, it will take more energy to heat even if you’re only using part of the room.
Some technology aiming to overcome this issue is Infrared heating. It’s basically like sunlight – it showers you with warm rays that heat you and the things around you, rather than the air. Some of these heaters emit light, like the pub garden heater variety, but some don’t and just look like a panel on the ceiling or wall. There are even options that look like mirrors or artwork.
This technology has been around for a while but not so much in residential properties. I’m keen to see how this one develops as it could be a useful way to limit the heating energy needed for larger spaces.
Besides cost there’s some physics to consider. Most houses have a standard electricity supply with a 100 amp fuse which is fine if all you’re powering is some lights, the TV and a kettle, but as soon as the whole house becomes electrically powered the 100amp limit could soon be reached. This would certainly be the case in a large property that would need many electric heaters.
Older buildings were draughty, which might not have been too warm but it helped to keep the building ventilated avoiding damp issues. Around comes double glazing and everyone upgrades, keeping their home warmer but also increasing the air tightness, increasing the risk of damp. Then the old boilers are replaced with efficient sealed units and the fireplaces are all blocked up. The result is a warm but damp building.
So the common solution to this? Drill a load of holes in the wall to allow for ventilation. This does help but it will also take all of the hot air in the room out with it!
One thing we should be looking to do is make buildings more air tight, modern windows are much better than the earlier double glazed units which will now be at the end of their lives. Doors should be well sealed and the fabric of the building made to be as leak-free as possible.
The theory is that a really well sealed and insulated building will not have damp issues because it will retain the warmth and keep the dew point higher. This is one of the key principles of Passivhaus design. In some older buildings this is easier said than done, so there might need to be some assistance in keeping the building free of damp. This is where a mechanical heat recovery ventilation (MHRV) comes in. The system will extract ‘stale’ air from the rooms with high humidity (such as the bathroom and kitchen) and pumps fresh air in from outside to the other rooms, creating a well ventilated building. As the stale air is extracted, the heat is removed from it and passed, through a heat exchanger, to the fresh incoming air, meaning there is a constant replacement of the air without losing any of the heat.
There’s also systems that recover heat from the drains and bring it back into the hot water system – so the warm bath water doesn’t go to waste. This isn’t too common at the moment though.
At this point in time, with high energy prices and heat pump technology still relatively cost prohibitive, the best thing any building owner can do is to insulate their building well.
The majority of buildings are built to the building regulations of the time. This is quite infuriating as the regulations are a legal minimum, not a target. We should be aiming to surpass these regulations rather than barely meet them.
Regardless of how your building is heated, keeping the heat inside the building is the best thing to do right now, keeping the bills low and the occupants comfy. Increase insulation in the roof, fill the wall cavity and look at additional external or internal insulation.
As a nation our buildings are stupidly under-insulated and we need to change this before anything else. We should be looking to our Nordic neighbours to learn how to keep our buildings warm.
Featured image by Erik Mclean from Unsplash