Listed property and EPC rating

QWe have an old cottage listed by association with our Grade II property in a conservation area, and it needs to be upgraded to a higher EPC rating.we are doing a thorough upgrade, new bathroom, new kitchen, new heating system, wiring and some damp proofing as we have some rising damp issues.

The walls are solid, about 16 inches thick, and built of local ham stone.we would like to insulate the walls internally, as long as it is not too thick. It is only a small two-up-two-down property.we are engaging a planning consultant and architect to draw up some plans for us, once lockdown is over, and would like some advice as to what we could or would be permitted to do.we have not been able to find any local insulation companies to give advice.

ANN & KEN, GLOUCESTERSHIRE

I would begin by questioning the basis on which you believe your cottage needs to be upgraded to a higher Energy Performance Certificate (EPC) rating. It is true that under the Minimum Energy Efficiency Standards (MEES), if you plan to rent out a domestic property it is now illegal to do so in England and Wales with an EPC rating below E. Importantly, however, government guidance states that an EPC is not required for a listed building or building in a conservation area if compliance with minimum energy efficiency requirements would ‘unacceptably alter’ the property’s character or appearance. In these circumstances, you could let it out with an EPC rating of F or G.

The problem is, though, that you cannot ascertain whether compliance with minimum energy efficiency requirements would unacceptably alter the character or appearance of your property without knowing what the recommended improvement measures are, i.e. unless you commission an EPC assessment. One way forward is to commission a draft EPC to establish whether the measures recommended entitle you to register for an exemption (consulting a conservation-accredited architect/surveyor and your local authority’s conservation officer, if necessary). Some recommendations will probably be unobtrusive and can be implemented beforehand (after, of course, obtaining any necessary listed building consent).

Should you ultimately proceed with insulating your cottage’s walls and have obtained listed building consent, proceed with care. The Society for the Protection of Ancient Buildings (SPAB) has recently completed over 10 years of research showing that industrystandard software overestimates heat loss (U values) through uninsulated solid walls, which commonly leads to them being excessively insulated using thick, impermeable material. This in turn increases the likelihood of dampness, which is associated with timber decay and mould growth, and can aggravate medical conditions such as asthma. Where more accurate U values are taken as the starting point, this broadens the scope for using more modest amounts of vapour permeable insulation – for instance, wood fibre or cork board – without these risks.

It’s strongly advisable to carry out practical, routine maintenance first. Damp walls are cold walls so do seek impartial advice on accurately diagnosing and addressing your dampness issues (remembering that rising dampness is much rarer than commonly supposed). Consider also ‘quick wins’, such as installing energy efficiency lighting or draught proofing windows.

DOUGLAS KENT, SPAB

If you want to find a qualified specialist then SPAB can suggest names over its free technical helpline on 020 7456 0916, weekdays 9.30am to 12.30pm, supported generously by Historic England. You can also visit www.spab.org.uk.