Why is one room always cold in our otherwise toasty dormer bungalow?

We have recently purchased a dormer bungalow which is very warm in general. However, our daughter's bedroom always seems to be colder than the rest of the house despite having double-glazed windows. It always seems to have a draught. The bedroom has two external walls with a window on one. However, the bedroom next door also has two external walls and doesn't seem to have the same issue. How can we find the cause and resolve the issue?

Dormer bungalows are typically subject to extremes of temperature: very hot in summer and cold in winter. In summer, heat absorbed by roof tiles or slates is radiated to the internal space. In winter, draughts remove heated air, leaving the rooms cold.

In most dormer bungalows I have surveyed there has been poor attention to detail in placing insulation and poor detailing when it comes to draughtproofing. Current building regulations require homes to be airtight. This is a measure that was not required previously, meaning older properties will by comparison be draughty. If one imagines that most attics are ventilated to prevent condensation, then it is typical that attic areas will be subject to draughts. Unless the internal habitable accommodation is adequately separated by way of insulation and draught proofing then the internal areas will be subject to excessive heat loss.

On a recent survey, I noted a similar situation to yours. One room was noticeably colder than others. On closer examination I noted that access doors were provided in this room allowing access to the eaves voids. These are the small attic areas located at dormer floor level and typically used for storage. The access doors were not draughtproofed. The attic areas were well ventilated and a strong breeze entered the room around the access doors. The temperature of each room will be dependent on the number of air changes per hour. If heated air is being rapidly replaced with fresh unheated air then room temperature will drop.

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In your case you should check for air leakage into the room from the attic. Check around any access hatches and check around light switches and sockets where these are placed on the lower dormer walls as these are areas where cold air can enter the room. It may be necessary to improve draughtproofing. Check within the eaves void and refit any loose or sagged insulation. Check that insulation has been correctly placed on the raking ceilings above the bedroom. There should be no gap below this insulation. Again, you should be able to see this from within the eaves void.

Check for any cold bridging or areas where insulation may have been omitted. Check also that air cannot travel below the dormer floor. Ideally air should not be permitted into this space as it can dramatically affect the room temperature by reducing the temperature of the floor structure. Check that the eaves void is not excessively ventilated and check that the external fascia and soffit boarding are in good condition.

As with the diagnosis of any defect you should start by checking out the more obvious or likely causes. If you’re still struggling contact your local chartered building surveyor. They specialise in the inspection of buildings and diagnosis of defects. Your surveyor can also advise with regard to efficient solutions and can direct you towards reliable tradesmen if you’re not into DIY.

Noel Larkin, is a chartered building surveyor and member of the Society of Chartered Surveyors Ireland, scsi.ie