Renovation Clinic:
Our experts answer your need-to-know heating questions, from boiler woes to updating heating systems and retrofitting underfloor heating and more
Your Heating Questions Answered
QWe’ve recently bought a home to renovate and we had hoped to keep the existing boiler as it’s relatively new. However, the hot water never stays at the right temperature for very long. Is the boiler the wrong size for the house perhaps?
ATIm Pullen sAys: If the boiler is too small it would be running for much longer than might be expected, which would be fairly obvious. And, it might never reach the desired temperature in the first instance.
You suggest that the water ‘never stays at the right temperature for very long’, and presuming there is a hot water cylinder, the implication is that the water does get to the right temperature, but is then used up. Therefore the cylinder size would be the first thing to look at. If it’s too small for the domestic hot water and space heating required by the household, it would cause this effect. It may be poorly
insulated, which again would have a similar effect. “The old copper cylinders were very inefficient, never large enough, with small primary coils (which gives a slow re-heat time), and bad insulation causing the cylinder to lose heat very quickly,” confirms heating specialist Brent Witherspoon of Chelmer Heating. In either case it would take a while for the boiler to catch up with demand.
Another possibility is the water consumption. Power showers, having more baths, and even having more people in the house, can use a great deal more hot water than the system was designed for and that could cause this effect. The solution would again be a bigger hot water cylinder.
With the information available it is really difficult to give a definitive answer. The best advice is to get a competent plumber in to check the system out. It is probably not the boiler, and that needs to be confirmed, but it could be the boiler set-up and/or the hot water cylinder. QWe’re hoping to replace the radiators in our home with underfloor heating. How disruptive will the work be?
ATIm Pullen sAys: It is always going to be disruptive. There are two options: conventional underfloor (UFH) which would be 40mm to 75mm thick and would go below the existing floor, meaning either excavating a concrete floor or lifting floorboards. The second option is a low-profile UFH system, like the NuHeat Lo-Pro system; these systems are less than 20mm thick and sit on top of the existing floor.
Low-profile systems generally allow you to deal with one room at a time, while conventional systems generally require the whole floor – throughout the house – to be dealt with at the same time. This is because conventional systems require a screed, be that either flow-screed
(which is the 40mm one) or a sand and cement screed (which is the 75mm one). In addition, the UFH pipework to each room or zone needs to be taken to a central manifold, and then connected to the hot water cylinder. There needs to be cabling for control systems installed and the pipework to the existing radiators taken out.
The low-profile systems are designed specifically for retrofit situations but as a standalone project there is still a lot of work to do and that can only upset the happy running of the house. Having said that, UFH does increase comfort, reduce running costs and open up more floor space. The advice would be to get two or three potential suppliers in and talk through exactly what has to happen. This will give you a better idea of the extent of the disruption and how long it is likely to last (bear in mind that it will always take longer than you are being told).
Q We want to replace our electric storage heaters with radiators and update our heating system. Where do we start, what’s involved, and how much will it cost?
A David Hilton says: As you have electric storage heaters you will have no pipework or radiators. Let’s assume you want to install a gasfired central heating system. First you will need to get the gas connected. A calculation will be done to determine the size of the meter required based on your maximum demand; the utility company will then provide a quote to install a pipe and meter.
The next decision will be whether to opt for a system boiler (with a hot water cylinder) or a combination (‘combi’) system that produces instant hot water and has no hot water store. If you have more than one bathroom it’s probably best to go for a system boiler. You will then need to plan where the pipes will run (either chased into a wall or boxed in within some form of surface-mounted trunking), as well as where the boiler and hot water cylinder (if you have one) will be installed.
The radiators can either be installed in a traditional parallel system, or to a manifold with separate pipes to each radiator. New boiler installations also need to comply with Boiler Plus regulations, meaning you will need some form of control for the boiler. As you are putting in a new system you can choose whether you want a wired or wireless control. Manifolds are easier to control as all the wires to the valves are in the same place, but you still need to have thermostats in the room. Alternatively, wireless systems can be installed that have battery-powered thermostats and you also have the option of battery-powered radiator valves for parallel radiators.
The cost of retrofitting a central heating system will depend on the scale of the project. A system boiler will cost around £700-£1,000, and a combination boiler will cost £900-£1,400. The installation of the boiler is around £1,500. A hot water cylinder will add around £700-£1,000 plus installation, which could also be up to £1,000 depending on materials and pipe runs. Installing radiators will cost around £500 per radiator as a generic estimate, but it is difficult to assume the pipe lengths and installation complexity. The controls may also cost around £100 per room.
If you are off mains, then an oil boiler would cost around £1,200 to £2,000, or an air source heat pump will be around £10,000 to £15,000, but you may be eligible for incentives that pay back a large percentage of the installation costs. Q We’re creating a new utility by converting one of the smaller rooms adjacent to the kitchen, and would like to install an electric underfloor heating system here. What are our options?
A dAvId Hilton says:
You can quite safely fit electric underfloor heating (UFH) to an existing floor but there may be an up-lift in the floor level, which could result in uneven thresholds. The ideal scenario is to excavate the floor and install some insulation (to reduce conductive heat loss) followed by a heat-resistant backing board or screed, before laying electric UFH. This is not always possible, and therefore it is worth shopping around as there are a number of different products that are aimed at different installation profiles.
The thinnest system (bestsuited to tiled surfaces) has wires attached to a thin mesh and the whole product is less than 2mm thick. The floor levels are not raised as the tile adhesive is applied directly onto the mesh and the heater then effectively sits in the adhesive layer. Expect to pay around £45/ m2 to £50/m2.
For fast installation (and costing around £55/m2 to £60/m2), a system with a matting can be used that
decouples the tiles from the subfloor. The matting is laid on the floor and the wires are pushed into preformed cut-outs. The adhesive is applied to the matting and, as it is not applied direct to the subfloor, potential future seasonal cracking risk is mitigated.
Soft finishes such as carpet, vinyl and laminate can be a challenge and foiltype systems are designed for this scenario. There’s no requirement for a screed with this type of solution and you can expect to pay around £40/m2 to £50/m2.
If the room is of an irregular shape or there are permanent fixtures, then a loose wire system is best-suited. The heater is a durable but flexible cable that is stuck to the backing boards and is embedded in the levelling compound or adhesive. Installation is a bit more detailed but the product allows for a lot more design layout variation. Expect to pay around £50/ m2 to £55/m2.
The cheapest system at around £15/m2 features a cable that is bedded in a screed. This system has thicker wires and allows for floor finish changes without damaging the wires. The system is slow to react and should be designed for longterm space heating and not for quick task heating for short periods of time.