Hello,
we have just taken over my mother’s house. The house has old windows, about 35 years old (PVC with double glazing). Since they do not close properly and some panes are frosted, we want to replace them.
The house was built in 1968 and has about 30 cm (12 inches) hollow concrete blocks with plaster on the inside and outside. The roof is well insulated. Insulating the exterior walls is not an option for now because it is almost unaffordable currently. The roof was recently redone and now has a photovoltaic system, as well as a new condensing boiler heating system.
We have received several offers, and each one recommends something different. What would you advise?
I am thinking of double glazing with trickle vents (because one apartment is rented out), or
triple glazing with vents in the windows, or
double/triple glazing without window vents.
Price is not an issue at the moment, but we want to avoid mold, especially in the rental unit.
Thanks in advance!
we have just taken over my mother’s house. The house has old windows, about 35 years old (PVC with double glazing). Since they do not close properly and some panes are frosted, we want to replace them.
The house was built in 1968 and has about 30 cm (12 inches) hollow concrete blocks with plaster on the inside and outside. The roof is well insulated. Insulating the exterior walls is not an option for now because it is almost unaffordable currently. The roof was recently redone and now has a photovoltaic system, as well as a new condensing boiler heating system.
We have received several offers, and each one recommends something different. What would you advise?
I am thinking of double glazing with trickle vents (because one apartment is rented out), or
triple glazing with vents in the windows, or
double/triple glazing without window vents.
Price is not an issue at the moment, but we want to avoid mold, especially in the rental unit.
Thanks in advance!
Mold develops when warm air condenses on cold surfaces and there is no airflow to dry it out. Since the old windows are probably not leaking enough to cause significant drafts, I believe that double or triple glazing does not influence the risk of mold. I know some window manufacturers say otherwise, but some of them lack even basic knowledge of physics. I cannot comment on ventilation, but if ventilation is used, it should only be with heat recovery. The window reveal, as the most critical area, can be insulated with silicate boards.
Whether double- or triple-glazed, regarding condensation on the wall, it makes no difference. Both offer better U-values than your 1968 hollow-block wall.
- Choose triple-glazed with warm edge spacers; 6-chamber profiles are more stable than the cheaper 5-chamber profiles with 68mm (2.7 inches) installation depth.
- If external wall insulation is not an option, I would recommend internal insulation using aerated concrete boards or wood fiber insulation boards, 6-8cm (2.4-3.1 inches) thick, especially if renovation work is planned inside anyway.
- Otherwise, at least insulate the reveal with 2cm (0.8 inches) wood fiber to prevent condensation and mold growth, and replace the interior window sills with wooden ones to reduce thermal bridging there as well.
I would choose windows without destroying the window rebate; that’s nonsense.
Instead, either install a simple exhaust system in the bathroom with continuous low-level ventilation (not just a loud on/off fan controlled by the light switch, but running continuously for minimum air exchange)
or install decentralized ventilation with heat recovery in the kitchen, bathroom, and living area. Avoid alternating supply and exhaust fans with pendulum operation; use individual units instead, e.g., Zehnder Comfo or models from Wolff.
Alternatively, when replacing windows, there are controlled/electric ventilators that can be integrated as frame extensions or hidden in the reveal area. I have no personal experience with these but am somewhat skeptical, as they create a continuous airflow similar to tilted windows at the reveal.
- Choose triple-glazed with warm edge spacers; 6-chamber profiles are more stable than the cheaper 5-chamber profiles with 68mm (2.7 inches) installation depth.
- If external wall insulation is not an option, I would recommend internal insulation using aerated concrete boards or wood fiber insulation boards, 6-8cm (2.4-3.1 inches) thick, especially if renovation work is planned inside anyway.
- Otherwise, at least insulate the reveal with 2cm (0.8 inches) wood fiber to prevent condensation and mold growth, and replace the interior window sills with wooden ones to reduce thermal bridging there as well.
I would choose windows without destroying the window rebate; that’s nonsense.
Instead, either install a simple exhaust system in the bathroom with continuous low-level ventilation (not just a loud on/off fan controlled by the light switch, but running continuously for minimum air exchange)
or install decentralized ventilation with heat recovery in the kitchen, bathroom, and living area. Avoid alternating supply and exhaust fans with pendulum operation; use individual units instead, e.g., Zehnder Comfo or models from Wolff.
Alternatively, when replacing windows, there are controlled/electric ventilators that can be integrated as frame extensions or hidden in the reveal area. I have no personal experience with these but am somewhat skeptical, as they create a continuous airflow similar to tilted windows at the reveal.
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