Trickle Vent Wizard
Not sure which trickle vent you need?
This quick helper is for existing fitted windows. We’ll guide you through it step by step – friendly, simple, and no confusing jargon.
Quick lesson: what’s an “opener” or “sash”?
The opener (also called a sash) is the moving part of the window that opens. So if your window has one section that swings open – that’s 1 opener. If it has two separate sections that open – that’s 2 openers.
Tip: Ignore the fixed glass that never opens — we only count the bits that actually move.
How many openers (opening sashes) are there in the room?
1 Opener
With one opening sash, airflow is more limited – so the trickle vent needs to do the job properly.
What counts as an opener (sash)?
The opener/sash is the part that moves. If you can unlatch it and it swings/tilts — that’s an opener. The fixed pane that never moves does not count.
Where is the opener?
2 Openers
Two opening sashes usually means better natural airflow, so you can spread background ventilation more evenly.
What counts as an opener (sash)?
Only count the sections that actually open. If your window has two separate moving parts, that’s 2 openers.
✔️ Most common setup: one trickle vent per opener
✔️ Usually fitted into the head of each opening sash
3 Openers or More
With multiple opening sashes, you’ve got plenty of airflow potential. The aim is steady background ventilation, not a gale through the house.
What counts as an opener (sash)?
Count each separate moving section that opens. Three or more openers means you can spread vents across the room.
✔️ Spread vents across the openers
✔️ Smaller vents per sash often feel better than one big vent
Single Top Opener
Top openers are ideal for a trickle vent – warm, moist air rises, so this setup is great for condensation control.
What’s an opener (sash) again?
The opener/sash is the moving part of your window. If it unlatches and opens, that’s the sash.
✔️ One correctly sized trickle vent
✔️ Fitted into the head of the opening sash
Single Side Opener
Side openers still benefit hugely from a trickle vent – especially in bedrooms and living rooms where condensation builds up overnight.
What’s an opener (sash) again?
The opener/sash is the moving part. Fixed glass that never opens doesn’t count.
✔️ One background trickle vent
✔️ Helps prevent black mould around the frame and reveals
Final Step: Vent length (bigger usually = more airflow)
Here’s the simple rule:
✅ Longer vents usually allow more airflow
So if your window can fit a bigger length, it’s often the better choice for condensation and mould.
Aim for the biggest size you can comfortably fit on your opener – without fouling handles, hinges, or the frame shape.