Tuesday, February 17, 2009

What the Victorians Didn't Do for Us - Part 5


Originally, the windows would have been timber sash windows with the frames rebated into the brickwork. Like most Victorian joinery these would have been painted with a lead-based gloss paint - most likely white. The rebates (the inner opening is stepped back half a brick and the frame partly concealed by half a brick on the outside) help to protect the timber from weather exposure, and also hide the bulk of the boxed frame containing the pulleys and weights for the sashes. The openings have a stone sub-cill which casts water away from the window and the brickwork immediately around it - in this case these have been painted white. At the back of the house the openings are capped by brick arches in red brick. To the front there are stone arches above the windows treated similarly to the cills.

Sometime in the mid-80s the timber windows on our house were replaced by the previous owner with UPVC windows like the one in the picture above. Typically these have a maximum design life of around 20 years, and after that they begin to fail. In our case the ironmongery has started to fall off (handles are rivetted through the plastic and when these fail they can't be replaced), the glazing panel seals are deteriorating and some of the opening mechanisms have buckled (not particularly strong in high winds!). So one of the major tasks and expenses of doing the house up will be replacing all of these.

Interestingly these windows have much smaller frame sections than the originals would have had. So the original internal openings must have been boxed out for the new windows to sit properly in the external openings. Having tried fixing curtain rails etc internally I think that this has probably been done with plasterboard and newspaper! So another task once work begins is to determine exactly what has been done around the openings internally.

Of course replacement timber sash windows are expensive and are prone to the same problems that the original windows would have had leading to their replacement. In terms of the current regulations, the main issues are insulation, solar gain, ventilation and maintenance. The UPVC windows are awning casements (which tend to catch the wind!) and double-glazed. These days even this would not pass muster for Building Control, and better glazing, possibly with better frames would be necessary.

My own preference is to return to sash windows. Party this is on aesthetic grounds, but also because I think that ventilation is much better controlled with them than using trickle vents.
Getting a timber frame that will take double glazing means beefing up the frames for the extra depth, so these will always appear slightly bulkier than the Victorian originals which were single glazed with putty. The other alternative is to resort to UPVC or metal sashes or composite timber windows.

UPVC is still the cheapest option, but the sections are bulkier and it always looks like, well, plastic. Metal is problematic because it is a poor insulator. Composite timber windows are a good compromise, being virtually maintenance free, but more expensive than UPVC. These are timber windows with seals and thermal breaks which are clad in coated aluminium externally. If installed properly they have a long design life, and still give the feel of a timber window without the expense of repainting/ restaining every 2-3 years which a normal timber window would need. In my experience almost no-one bothers repainting until it is necessary (paint is falling off or the timber is rotting), by which stage the timber needs repairing as well.

While looking around at windows I did a quick count on our street. Out of roughly 100 houses nearby, about 90% had gone for the cheap UPVC option - in most cases doing away with sashes altogether. Within this there were virually no repeats, which reflects the number of manufacturers out there, I guess. They were also all uniformly plastic white. A couple had timber framed windows that were not sashes - these were probably installed in the 1950s, and about 2 had original sashes or very close reproductions of these. Strangely enough, when we moved here we looked at another property on the same street which had remained untouched since the 1930s. This one had the origial sashes, which were painted a dirty yellow/cream colour. These have now gone and the house has been renovated.

Anyway, getting back to our windows, my current thinking is to go with timber composite frames. These have a good thermal performance, negligable maintenance, can be made as sashes with glazing bars and house the latest thinking in double-glazing (special glasses with inert gas filling the cavity between panes). The other advantage that these have is that they are dimensionally stable - timber windows can warp and stick when their moisture content varies. This also helps with draft-proofing. The Scandinavians and Americans seem to have cornered the market in these, and 2 of the more well known companies are Marvin and Velfac. Of these Velfac doesn't do sashes, so if anyone knows of other manufacturers who do composite sashes drop me a line here.

1 comment:

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