Double or triple glazing: which do you need?

What is the practical difference between double and triple glazing?

Triple glazing has three panes of glass in the unit instead of two. In practice that means more heat kept in than the double glazed version of the same window.

The catalogue makes the comparison easy because the double and triple glazed windows come in the same styles and sizes, from 440mm x 610mm up to 1770mm wide and 1190mm high. You can compare one size across the two ranges, and a triple glazed window of a listed size fits the same opening as the double glazed one.

What does triple glazing do about heat?

A third pane keeps more heat in than two panes do. The glass is one part of the window, and the frame, the fit and how the frame is sealed all matter too.

Triple glazing suits cold rooms, exposed sides of the house, north facing rooms and rooms with a lot of glass, such as a set of French doors. Double glazing suits most rooms. For energy figures or a certificate for building control, ring 0151 525 4488 and ask what the manufacturer can supply. The double glazed windows are named A Rated and the triple glazed windows A+ Rated.

How do I compare prices?

Compare the two listings side by side on the product pages. Because you can compare like for like, you can choose triple for the rooms that suit it and double elsewhere. For the big sizes, such as the 1770mm pairs and the French doors, plan for two people to lift the larger units.

Where is triple glazing worth it?

Choose triple glazing for cold rooms and rooms large in glass, and double glazing for most other rooms. Typical places for triple are a north facing living room and a garden room with a big run of French doors.

• Triple glazing suits: cold rooms, big glazed openings, a door that opens onto an exposed side of the house.
• Double glazing suits: bathrooms, WCs and utility rooms with small windows, rooms that are already warm, and budget projects.

You can mix the two across the house, provided the colours and handles suit.

How do I compare the two ranges like for like?

1. Pick the style and size you need from the double glazed range.
2. Find the same size and colour in the triple glazed range. The names differ: the double glazed windows spell out Left Hand Side Hung, and the triple glazed ones shorten it to LH.
3. Check the glass, clear or obscure, is the same on both.
4. Compare the prices side by side on the two product pages.

What else matters besides the number of panes?

The frame, the fit and the glass type matter as much. Fit matters as much as the glass. The products come with a handle, a PVC cill and glazing packers, and the windows, single doors and French doors have trickle ventilation.

Choose clear or obscure glass for the room: obscure is for bathrooms and WCs, the listing for each size shows which glass it has, and the pairs come with clear glass. Choose the colour: white, or grey 7016 outside with white inside. Then get the size right with how to measure for uPVC windows and doors. All of these are supplied for your installer to fit. Replacement windows and doors are notifiable work, so use a registered installer or tell building control.

What does the catalogue offer in each?

Product	Double glazed	Triple glazed
Windows	Double glazed windows, named A Rated	Triple glazed windows, same styles and sizes
Single doors	Double glazed single doors, 840, 890 and 920mm wide	Triple glazed single doors, same widths
French doors	Double glazed French doors, with a 150mm cill included	Triple glazed French doors, same widths and heights
GRP composite doors	Double glazed	Composites are double glazed

Each range has the same number of listings: 174 windows, 48 single doors and 28 French doors. A listing is one size, colour, glass and hand, so the two ranges give you a like for like choice at every size. For the glazing on the sliding patio doors, ring 0151 525 4488. Samples to compare: the double glazed grey top hung window and the triple glazed grey/white top hung window, or the double glazed and triple glazed French doors. Everything is delivered direct by the manufacturer to your address, and delivery is priced by postcode.