How do we cut the energy costs in our period house?
Query: We would like to make our period house more comfortable and cheaper to run - but we're not sure what we can do to the building fabric. Can you help? Michael, Rathmines
Answer: A Period houses require more careful consideration than modern houses when interventions to make them more energy efficient and comfortable are proposed. Normally, they are of 'traditional construction', meaning that typically, they were built before 1920 with solid brick or stone walls and timber-framed roofs with natural slate or copper/lead finishes.
Before you make any changes, check the general maintenance and condition of the building. Poorly maintained windows and doors can be draughty. A wet wall caused by leaking rainwater goods or failed renders/pointing will conduct more heat and be colder than a dry wall.
Also consider the geometry of the house and actual areas of heat loss. If your house is in a terrace, the exposed area of walls may be quite low so you might look at other areas with a higher proportion of heat loss such as the roof.
Traditional solid single-leaf walls behave differently to modern construction in relation to environmental factors such as moisture absorption following rainfall. Thick traditional walls have the ability to absorb moisture and subsequently dry out in a way different to modern construction. This characteristic should be considered when you're choosing insulation materials for walls. Breathable insulation products such as wood-fibre and calcium silicate boards are available with good technical advice from the suppliers as to how the breathability and drying-out function of walls can be maintained.
Period houses may or may not be protected structures. If they are protected, some interventions may require planning permission. But the special interest and features of a house should be retained for future generations and the same conservation-led approach taken to protect them even if they are not protected. For example, internal wall insulation may be more appropriate in rooms without features such as cornices and window shutter boxes. Historic hand-made glass in original timber windows should ideally be kept. You could consider secondary glazing to retain the original character of the windows - it is now available in slim aluminium units that are openable and have minimal visual impact on the windows.
Insulation of timber suspended floors and roofspaces is an obvious area where upgrades can be made without affecting the character of the building. Ventilation paths to attic and floor voids should be maintained or possibly increased following the installation of insulation. Air infiltration can be a significant source of heat loss. If a suspended floor is being insulated, take the opportunity to reduce air infiltration and draughts around the floor with airtightness measures. Although the house will need a general level of background ventilation, this can be controlled by measures such as draught-proofing of traditional sash windows and installing dampers to open fireplaces.
Prioritise building services, ie, heating and hot water systems, as often you can make significant energy savings here with minimal impact. A new high-efficiency boiler can yield immediate energy savings. If the heating system is zoned, it means that hot water and heating to different bedrooms and living spaces can be controlled on separate time and temperature control.
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- Advice is for guidance only and readers are advised to seek professional assistance for any proposed project.
If you are considering changes to your home, work with a registered architect. You can find a registered architect on riai.ie, the registration body for architects in Ireland.
Fergal McGirl is a conservation architect with a special interest in energy efficiency in historic buildings; fmgarchitects.ie