Extensions & Conservatories
Extensions and conservatories expose a lot of glazing and surface, so they swing cold and hot. Better fabric, junctions and ventilation make them comfortable year-round.
Why is my extension cold and hard to heat?
Extensions are often colder and harder to heat than the original house because they expose more surface to the outside per square metre, usually contain a lot of glazing and roof area, and frequently have thermal bridges where the new structure meets the old. Add heating that was sized for the original home rather than the extension, and the room struggles to stay warm. The causes are specific and measurable — and fixable once identified.
Read the guideWhy is my conservatory too cold in winter and too hot in summer?
A conservatory is too cold in winter and too hot in summer for one underlying reason: it is almost entirely glass and roof with very little insulation or thermal mass. Glass lets heat out rapidly in winter and lets solar heat flood in during summer, with nothing to buffer either, so the room swings to extremes. Making a conservatory usable year-round means reducing those swings — improving the roof and glazing, controlling solar gain and ventilation — or accepting its limits.
Read the guideShould I replace my conservatory roof with a solid roof?
Replacing a conservatory's glass or polycarbonate roof with a solid, insulated roof is often the single most effective way to turn an unusable, baking-then-freezing conservatory into a comfortable year-round room — because the roof is usually where most of the heat is lost in winter and gained in summer. But it only delivers if the rest of the structure can keep up: the glazed walls, the floor and any dwarf walls also need to perform, and the existing base and frames must be able to carry and suit a heavier roof. So it is usually worth it, provided it is done as part of the whole picture.
Read the guideWhy is my single-storey extension so hot in summer?
Single-storey extensions — especially open-plan kitchen-diners — often overheat in summer because they combine the very features that admit and trap heat: large rooflights and glazed doors that pour solar gain in, a big flat or shallow roof fully exposed to the sun, and frequently limited ventilation with glazing on only one side. Heat gets in fast through the glass and roof and cannot easily be purged. It is a design-and-ventilation problem, fixable with shading, roof improvements and better cross- and night-ventilation rather than air conditioning.
Read the guideWhy is there damp or cold where my extension joins the house?
Damp, cold or mould at the line where an extension meets the original house is almost always a junction problem: the insulation and airtightness of the new build do not connect continuously with the old, leaving a thermal bridge and often an air-leakage path right at the join. That cold, leaky line then runs colder than the surrounding surfaces, so it attracts condensation and mould and feels cold. It is a detailing issue at the interface between old and new, not a coincidence, and it is fixed by making the junction continuous.
Read the guideWhy is my orangery or glass extension uncomfortable?
Orangeries and glass extensions are uncomfortable for the same reason they are appealing: they have a large area of glazing, which loses heat readily in winter and admits strong solar gain in summer, so the space swings between cold and hot far more than a conventional room. Glass has a much higher heat loss and far higher solar gain than an insulated wall or roof, so a room dominated by it is hard to keep at a steady, comfortable temperature. The discomfort is a predictable consequence of the construction, and it is addressed by reducing the heat loss and the solar gain — better glazing, shading, a more solid roof, and adequate heating and ventilation — once the dominant problem is identified.
Read the guideWhy is my extension getting condensation?
Condensation in an extension usually comes down to cold surfaces and inadequate ventilation, often concentrated where the extension meets the original house. Extensions present a lot of glazing and a large roof and wall area for their size, so they run cold if the insulation or airtightness is sub-standard; thermal bridges at the junction with the existing building create cold lines where condensation and mould form; and a new, well-sealed extension can trap moisture if it was not given proper ventilation. The fix is to find which of these dominates — cold fabric, bridging at the join, or a ventilation deficit — and address it, rather than just wiping the symptom.
Read the guideHow do I make my extension warm and comfortable?
Making an extension warm and comfortable year-round means getting four things right together: good, continuous insulation; a well-detailed, airtight junction with the original house; the right glazing for the amount and orientation of glass; and heating sized to the extension's real heat loss. Extensions are uncomfortable when one of these is weak — thin insulation or a cold junction makes them cold and condensation-prone in winter, while too much unshaded glazing makes them overheat in summer. The route to comfort is to assess the extension's heat loss and gains and fix the weak links, rather than simply turning up the heating in winter and suffering the heat in summer.
Read the guide