Thermopy Guide
Insulation savings and payback
See how loft, wall and window upgrades reduce heat loss and shorten heating bills.
Where heat escapes
Roofs, walls, floors and glazing dominate losses. Prioritize the weakest element first — often loft or single-glazed windows in older homes.
Model the upgrade
Use the Insulation Calculator to compare U-values before/after and translate reduced load into annual savings and payback years.
Prioritize loft vs walls
Loft or attic top-ups are often the fastest win for older homes: large area, accessible, and high heat loss. Cavity or solid-wall insulation usually costs more and takes longer to pay back, but can transform comfort once the roof is already decent.
U-values in plain language
U-value is heat flow through a construction (W/m²·K) — lower is better. Improving a cold roof from a high U-value toward modern targets cuts roof losses sharply. Compare before/after U-values in the Insulation Calculator instead of guessing from thickness alone.
Moisture and ventilation caveat
Tighter envelopes reduce heat loss but can trap moisture if ventilation is ignored. Plan vapour control, extract fans or MVHR where needed, and avoid insulating over unresolved damp. Comfort gains disappear if you create condensation risk.
Example payback
A loft top-up that costs €1,500 and saves €200–€350 per year often pays back in roughly 4–8 years depending on fuel price and climate. Solid-wall projects may run 10–20+ years on pure bill savings — weigh comfort and future heat-pump readiness too.
Combining upgrades
Stack draught sealing, loft insulation and better glazing before expensive plant swaps when possible. Lower heat loss unlocks lower flow temperatures for heat pumps and smaller radiators — model combined packages, not isolated measures.
Next step with the Thermopy calculator
Enter current and upgraded U-values, heated area and fuel tariff in the Insulation Calculator to see annual savings and payback years, then decide which measure to schedule first.
Get exact numbers with our free calculator
Use your room data, climate and energy rates to generate actionable results in minutes.
Open calculatorFAQ
Which insulation gives fastest payback?
Loft top-ups and draught sealing often pay back quickly; solid-wall insulation has longer horizons but big comfort gains.
Do I need a survey?
A survey helps for damp or heritage buildings, but online estimates are enough for initial budgeting.
Will insulation help AC too?
Yes — better envelopes reduce both heating and cooling loads year-round.
Are grants or incentives available for insulation?
Many regions offer loft, cavity or whole-home retrofit support, but eligibility and amounts change. Check local schemes and always run payback with and without incentives so the project still makes sense if funding is delayed.
DIY loft top-up or hire a professional?
Competent DIYers can top up accessible lofts if they respect depth, coverage at eaves and safe walk boards. Hire professionals for damp issues, complex roofs, solid walls, or any work that affects fire stopping and ventilation strategy.