Secondary Glazing for Hay Fever, Pollen and Air Pollution
Dr Sarah Chen
Building Physics Consultant
Old sash and casement windows rarely fit tightly. Gaps around the frame let in cold air in winter, and in spring and summer they also let in pollen, street dust and fumes from busy roads. For people with hay fever, allergies or asthma, and for parents of young children, sealing those gaps can make a noticeable difference indoors.
Secondary glazing is not a medical treatment, and it is no substitute for advice from a GP. But it does tackle one of the easiest routes for outdoor particles to get inside.
How Secondary Glazing Keeps Particles Out
A secondary unit is fitted inside the existing window with brush seals and gaskets around its edge. When closed, it creates a second barrier behind the leaky original frame. Air, and the pollen and dust it carries, can no longer drift through the gaps as easily.
- Pollen: grass and tree pollen is carried on air currents and enters through any gap. Fewer gaps means less indoor pollen.
- Street dust and soot: homes on main roads and bus routes often find a film of grime on window sills. Sealing the window reduces it.
- Traffic fumes: secondary glazing will not filter the air, but it reduces uncontrolled draughts carrying fumes from the road.
Keep Ventilation Under Control
Sealing windows means you need to ventilate on purpose. Use extractor fans in kitchens and bathrooms, trickle vents where fitted, and open windows at times of day when pollen counts are lower. Controlled ventilation also prevents condensation; see our condensation guide.
Practical Tips for Hay Fever Season
- Keep the secondary panes closed on high pollen days, especially on the windward side of the home.
- Air rooms briefly instead of leaving windows open all day.
- Wipe sills and tracks regularly so trapped pollen does not build up.
- Consider a HEPA air purifier in bedrooms alongside better windows.
The Noise Bonus
Homes on busy roads usually suffer from noise as well as fumes. The same unit, fitted with acoustic laminate glass and a good air gap, can cut traffic noise substantially. See sound insulation and our guide to traffic noise in London flats.
Frequently Asked Questions
Does secondary glazing help with hay fever?
It can reduce how much pollen gets indoors through leaky windows, which many hay fever sufferers find helpful. It does not remove pollen already inside.
Will it make my home stuffy?
Not if you ventilate deliberately. Openable secondary glazing lets you air rooms whenever you choose.
Can secondary glazing go on listed or period windows?
Yes. It is fitted inside and is usually reversible. See listed and heritage properties, or get a free quote.
