The 1 Mistake You’re Making with Your Sash Windows in a Heatwave – And It’s Sending Your Energy Bills Soaring
The 1 Mistake You’re Making with Your Sash Windows in a Heatwave – And It’s Sending Your Energy Bills Soaring
When a heatwave hits, most of us instinctively fling open our windows and let the air in. It feels refreshing — at least for a while. But here’s the catch: if you leave your sash windows open all day during hot weather, you could be making your home harder to cool, forcing fans and air conditioning to work overtime, and sending your summer energy bills through the roof.
Why Open Windows Can Work Against You in a Heatwave
In hot, still conditions, open windows often do little more than let warm air seep in and cool air escape. By mid-afternoon, your home’s interior can actually be warmer than if the windows were closed, blinds drawn, and ventilation managed strategically.
Traditional double glazing in restored sash windows can help, but in extreme heat, it often struggles to keep internal temperatures stable. The sun’s radiant heat still penetrates through the panes, and older timber frames can leak cool air.
How Vacuum Glazing Keeps You Cool
Fineo vacuum glazing is a breakthrough for heritage windows. By replacing the air (or gas) gap in traditional double glazing with a near-vacuum, heat transfer is drastically reduced. This means:
Up to 8 times better thermal insulation than single glazing — without altering your original sash frames.
Better performance than standard double glazing, keeping your home cooler in summer and warmer in winter.
Minimal impact on the appearance of period windows, preserving their character while upgrading comfort.
In a heatwave, Fineo glazing slows down the rate at which external heat seeps indoors, meaning you’ll rely less on fans, portable coolers, or air conditioning — all of which can be costly to run.
Summer Sash Window Prep & Maintenance Tips
Even with high-performance glazing, a little seasonal care goes a long way. Before temperatures spike:
Check seals and draught-proofing – Any gaps in your sash frames will allow hot air in and cool air out.
Inspect cords and pulleys – Smooth operation means you can open and close windows strategically for night-time cooling.
Clean and maintain timber – Well-painted, healthy frames resist swelling or sticking in humid weather.
Use blinds or shutters – Closing them during peak sun hours can block up to 75% of solar heat gain.
Ventilate wisely – Open windows at night or early morning when the outside air is cooler, then close them as temperatures rise.
Why Traditional Double Glazing May Not Be Enough
While standard double glazing offers some protection, it doesn’t match vacuum glazing’s ability to regulate temperature during extreme weather. With rising global temperatures and more frequent heatwaves in the UK and Ireland, investing in a glazing solution that works year-round is becoming essential — not just for comfort, but for controlling household energy costs.
Bottom line: In summer, it’s not about keeping your windows open all day — it’s about keeping the right heat out and the right cool in. Fineo vacuum glazing lets you enjoy your period sash windows without compromising on comfort, efficiency, or heritage charm.