Thermal Performance

Warm Roof U-Values Explained For Homeowners

Written byGraham Sutcliffe, Project Management Specialist

A U-value measures how much heat passes through one square metre of a building element for each degree of temperature difference. Lower numbers mean less heat loss.

What U-value should a conservatory roof have?

A replacement conservatory roof in Scotland should achieve 0.15 W/m²K or better when the room is treated as heated living space.

Scottish building standards set target U-values for roofs in new work. Reputable warm roof systems are specified between 0.13 and 0.18 W/m²K depending on insulation depth.

Element	Typical U-value	Effect
Polycarbonate roof	2.6 W/m²K	Very high heat loss
Glass roof, standard unit	1.6 W/m²K	High heat loss
Glass roof, low-e argon	1.0 W/m²K	Moderate heat loss
Insulated warm roof	0.15 W/m²K	Low heat loss

Do windows need to match the roof?

Windows should achieve 1.4 W/m²K or better, because glazing becomes the weakest element once the roof is insulated.

How do I verify the specification?

Ask the installer for the system manufacturer's U-value certificate and the insulation thickness in millimetres.

Manufacturer name and system reference
Insulation type and thickness
Certified U-value in W/m²K
Ventilation and condensation detailing

Related guides

Thermal Performance

Why Your Glasgow Conservatory Is Too Cold In Winter

Planning & Warrants

Building Warrants For Conservatories In Glasgow

Base & Structure

Conservatory Bases And Foundations In Scotland

Interior of an insulated warm roof conservatory in winter

Planning a conservatory in Glasgow?

Get a fixed written quotation

Send us your postcode and a rough idea of size. We will confirm whether a building warrant applies, specify the roof and glazing, and send a fixed price in writing.

Speak to a surveyor

We survey across Glasgow and the surrounding council areas. Mon–Sat, 8am–6pm.