The glass in windows is the least efficiently insulated aspect of the house, and the only way of cutting the heat loss while still being able to see out is to add another layer of glass. Double glazing can be clone in two ways: existing panes of glass can be replaced with special double-glazed panes called sealed units, or a second pane can be installed inside the existing one so-called secondary glazing.
Secondary glazing is the only practical course of action unless the existing windows are being completely replaced. There are dozens of types available for do-it-yourself installation, providing hinged and sliding inner panes that blend in well with most types of window; similar systems are also available from professional installers. The panes are either fixed to the window frame itself, or else fit within the window reveal on special track. An effective but flimsy alternative is clear acetate or PVC (vinyl) film fixed to the inside of the frame with double-sided tape.
Apart from reducing heat losses through the windows, double glazing eliminates ‘cold spots’ in the room next to the windows. It also helps to reduce noise penetration from outside as long as the inner panes are kept closed. It will reduce condensation too, but only if the inner panes are well sealed to their track to stop wants moist air getting into the air gap between them and the window itself. Lastly, lockable types will give a measure of additional security; burglars may tackle one pane of glass, but many will flinch at two.
As far as external doors are concerned, solid doors offer better insulation than glazed ones, so go for this type if planning a replacement. If a glazed panel is a must, choose one with a sealed double glazing unit using safety glass. I lent loss through any external door can be reduced by building a porch outside it, to create an airlock between the house and the outdoors.
Fitting Sliding Units
- Measure the height and width of the window reveal at each side. If the figures differ, work fronts the smaller measurements to its height and width.
- Cut the track sections to length with a fine-toothed saw and sand the cut ends smooth. Make cut-outs following the kit instructions to form corners.
- Offer up the side track sections and screw them in place. Use thin packing to get them truly vertical if the walls are out of square
- Next, secure the top track section in place. Screw it directly to a wooden lintel or pre-drill holes in concrete ones and inset wall plugs first.
- When positioning the bottom track on the windowsill, use a straighted edge and a spirit level to check that it is perfectly aligned with the top rack.
- Measure up to the glass as directed in the kit manufacturer’s instructions, and order the glass. Fit cut lengths of glazing gasket to the edges of each pane.
- Fit the first pane into the track by inserting its top edge in the top channel, and then lowering its bottom edge. Repeat the procedure for any remaining panes.
Fitting Thin-Film Double Glazing
- Start by sticking lengths of double-sided adhesive tape to the window frame, about 1/2in from the surrounding masonry.
- Press the files on to the tape, pulling it as taut as possible. Then play hot air from a hair-drier over it to tighten it up and pull out any wrinkles.
- When you are sure the film is even and wrinkle-free, trim off the excess film all the way around the window using as harp utility knife.