Ask our architect

Presenter of Channel 4’s The Home Show and Restoration Man, George Clarke solves your design queries and provides professional architectural know-how 145 GDS 1111

I’m currently designing a new house and am interested in installing a ground source heat pump system. Are there any considerations with regard to the best types of radiators?

To be honest, if I’m installing a ground source heat pump (GSHP) my preference is to do away with radiators. The ideal arrangement is a well-insulated property with a wet underfloor heating system. GSHPs raise the temperature of the water in the system to around 40°C, which is perfect for underfloor heating systems. Having no radiators is also a space saver in your home giving you more wall space for storage; it also makes it easier to plan a room and arrange furniture. You can use radiators rather than underfloor heating with a GSHP, but they have to be low-temperature models, which require temperatures of between 30°C and 35°C. Conventional radiators need higher temperatures of around 60°C to 80°C, so you would have to use a GSHP in combination with a conventional boiler or immersion heater, which defeats the point if you’re trying to be as ecological as possible. See and for more on GSHPs and low-temperature radiators.

Which is hardest to deal with; wet rot or dry rot? We’ve got both!

If you have both then you are in the premier league of rot attack! Wet and dry rots are both the result of a fungus attacking damp timber. Wet rot is more common and affects timber with a moisture content of more than 24 per cent. This can occur if water has leaked from sinks and baths, in poorly maintained roofs or when timber is in close proximity to wet or damp walls. The good news is that wet rot is relatively easy to get rid of. First you have to work out where the damp is coming from, repair the source of the problem and prevent any more moisture coming into the property. Damaged timber has to be cut out and replaced with new treated timber once the area has dried out – you may need to increase ventilation if the rot is in an enclosed space. Dry rot, on the other hand, is one of the most damaging conditions that a building can suffer from. It affects timber with a lower moisture content of between 18 and 20 per cent, and is a frightening problem as the rot can travel through masonry. Dry rot spores will develop into a soft cotton wool-like form and when the fungus has used all of the nutrients in one length of timber it will travel through masonry or plasterboard in search of its next meal. But, dry rot can be treated. First you need to stop the source of the moisture then remove and replace the damaged timber. Any masonry in contact with the fungus, and this includes the soil below ground-floor timbers, needs to be thoroughly cleaned, and treated with a masonry steriliser, or biocide. Thick walls will need drilling so that the biocide can be injected. All surrounding timbers need to be sprayed with a biocide to ensure that any traces of the fungus are killed. Dry rot can be frighteningly disruptive and can cost a small fortune to put right, so I wish you all the best with your repairs.

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