Ventilation for double glazed units

[LyNx]

With wooden frames, misting occurs when the sealed units are not drained properly. It can also happen if the perimeter of the sealed unit is not ventilated effectively. In most cases the fault is repairable. Sometimes, though, you may need to replace the unit.

Just been reading up on U values for double glazed units and came across this quote.

I plan on using a dry glazing method for some doors. I've been thinking about using these items. With the easyclip fitted around the rebate, will this allow for the ventilation required.

http://www.reddiseals.co.uk/acatalog/Easyclip_Base_for_24mm_Unit.html

http://www.reddiseals.co.uk/acatalog/EPDM_Glazing_Tape.html

or

http://www.reddiseals.co.uk/acatalog/EPDM_Tape_with_lip.html

Can anyone who has used a dry glazing system comment on if pros and cons?

Thanks

 

[ike]

Hi Andy,

With wooden frames, misting occurs when the sealed units are not drained properly. It can also happen if the perimeter of the sealed unit is not ventilated effectively. In most cases the fault is repairable. Sometimes, though, you may need to replace the unit.

Sealed units are what they say i.e. sealed. Misting occurs when the seal (the urethane mastic around the edge) is compromised. The spacer strip seperating the glass contains clay dessicant beads. Once they get saturated, the misting occurs. Faulty DG units are technically repairable but invariably uneconomic to do so. Replacement is the usual option.

The gap between the unit and the frame is for three reasons,

(i) it provides for the dimensional tolerance of the unit.

(ii) it allows adjustment using the glazing packers you refer to in order to locate the unit within the frame. The unit acts to brace the frame and in the case of an opening light - prevent it lozenging with the weight of the unit.

(iii) allows for movement due to expansion.

The glazing tape cushions and seals the unit to the frame and helps to minimise water ingress into the cavity between the unit and the frame. It's unlikely to seal 100% hence some provision for drainage at the bottom of the frame to the outside.

So glazing packers and glazing tape is established practice. Window fitters use a dab of silicone adhesive sealant to secure the packers in place after fitting the unit. Without it they would tend to slip out of position over time and suddenly your window won't open and shut properly.

PS 'Low E' units must be fitted with the coated pane outermost. The low E coating is on the inside of the outer pane.
cheers,

Ike

 

[LyNx]

Thank you for the info, very helpfull

PS 'Low E' units must be fitted with the coated pane outermost. The low E coating is on the inside of the outer pane.

I take it that it's marked up, or noticeable?

 

[ike]

I'm not sure if the panes are marked, etched or labelled. You can see which pane has the coating by looking at a shallow angle which enhances the reflective tint.