Articles published in 2015
Glazing
The materials from which glass are made are abundant. Plate glass is made from 70% silicon dioxide (sand), 14% sodium carbonate (washing soda), and 10% calcium oxide (lime). These combine together at a high temperature, 1600°C, to form soda-lime glass.
The biggest manufacturer of glass in the UK, for both buildings and vehicles, is Pilkington. They have a long history. They started as a partnership in 1826, and became a limited company, Pilkington Brothers, in 1894. During the 1950's they developed the float glass process for making plate glass. In this, molten glass is floated on a bed of molten tin at 1000°C, and after the glass has been drawn off, it has perfect surfaces. (Prior to this, plate glass had to be ground flat and then polished.)
Daylighting
Daylighting is the prime purpose of windows. Giving a view and harvesting solar energy are secondary.
A common daylighting problem is getting sufficient light to the back of a deep room on a dull day. There is an internationally defined 'CIE overcast sky' for which a mathematical equation defines the hypothetical variation of brightness in the sky when the sky is overcast. (CIE = 'Commission Internationale d'Eclairage', ie, International Commission on Illumination.)
Materials For Window Frames
Wooden Frames
Redwood pine is the usual material. The slow growing pines from the cold climates of Scandinavia and Russia are preferred.
Solid timber can be a little unpredictable in use, so wood frames may be made of 'engineered wood' for more stability.
More About Windows
My May article was about the choice of materials for window frames. As your selfbuild is likely to outlast you, you may be concerned about the longevity of its frames – glass, of course, lasts indefinitely. Here are some very approximate estimates for the life expectancy of different frame materials:
uPVC 25-35 years
Softwood, fibreglass 40 years
Aluminium 45 years
Modified softwood 60 years
Hardwood 70 years
Exterior Doors and Doorsets
The front door of your home gives visitors an impression of the style to be found within. Is your aspiration modern, post-modern, olde worlde, or what? For many selfbuilders, a front door that combines elegance with sturdiness is ideal.
Interior Doors
There is a wide choice of style and substance for interior doors.
Flush doors
These doors have flat facings of plywood or hardboard, and they are the cheapest type of door. They are usually painted, either in the factory or on site.
At little extra cost, some flush doors are finished with a foil veneer that imitates wood. A real wood veneer is another possibility, though this does increase the price substantially.
The cores of these doors are either honeycombed card (lightweight) or solid panels.
When fitting flush doors, look for the 'Lock block' stamp – fit the hinges on the other side!
Window Energy Ratings
It used to be standard practice for house builders to build in window frames as the walls were built, and to glaze the windows later. But it is becoming increasingly common for the walls to be built with openings for the windows, and for factory glazed windows to be fitted later. So pre-glazed windows are becoming much more common – especially as Continental windows, which are invariably pre-glazed, become more popular.
Many ranges of pre-glazed windows have been given a Window Energy Rating. Note that this rating applies to the range of windows, and not to any particular window within the range. The intention is that Window Energy Ratings enable a comparison to be made of the energy performance of different ranges of pre-glazed windows.
Windows: An Introduction
Saxon churches had glazed windows, but glass was not available to the general population. To let light into a home, there would be slits in the walls. (The word 'window' is said to be derived from the Norse for 'wind eye'.) By the Middle Ages, glass had become affordable to the wealthy – the slits were wider and glazed with many small panes of glass. (This was crown glass, sometimes with the familiar 'bulls eye'.) Poorer people made do with oiled cloth, or the like, that allowed in some light while keeping out the wind and rain. (Needless to say, people spent much less time indoors in those days.) But by the Victorian era, mass production of plate glass had resulted in windows with large panes becoming commonplace.
Voting For Selfbuild: And for custom build too?
With a general election imminent and the political parties making many promises for the future, I thought it would be useful to have a look at some of the old, 2010 Manifesto promises and, more importantly, at what the out-going Coalition government actually did do to help people who want to build their own homes.
The UK has a peculiar house building industry in which national house building companies dominate the industry – probably because they gain by far the greatest share of land with planning permission. These companies resist change. In contrast, selfbuilders are much more welcoming to innovation.
Windows and the Building Regulations
Surprisingly, the building regulations have nothing to say about the prime purpose of windows, namely daylighting. Perhaps the rationale is that there will be at least minimal daylighting if the windows accord with the requirement for purge ventilation (in Part F of the regulations, Ventilation). Or perhaps, common sense has been allowed to trump the complexity that would be involved in attempting to regulate daylighting.
More About Exterior Doors
In a recent article about windows, I mentioned that in Britain and Scandinavia windows have traditionally opened outwards. In Scandinavia, exterior doors, too, open outwards. Not so in Britain – a visitor standing at a front door would be shocked to have it opened into his/her face.
(A possible reason for the opening outwards was offered by a Swede on the Green Building Forum: In Sweden it used to be the practice for houses to have double doors for better thermal insulation. Necessarily, the outer door opened outwards, and the inner door inwards. Double doors are no longer used, but the practice of outward opening doors has remained.)
Out Goes The 2016 Zero Carbon Target: And in will come the 2020 nearly zero-energy directive, maybe
With 2016 nearly upon us, I thought it might be worth reflecting on the life and death of the 2016 Zero Carbon Target for new housing.
The target was set in 2007 by the Labour government with all party support. By 2016 all new homes were to be 'zero carbon'. Over the course of a year, net emissions of carbon dioxide resulting from all the energy used in the home would be zero – or more likely, negative. (The home would be a net contributor of electricity into the grid.)
The target was to be achieved by progressively reducing the Target Emission Rate in the Standard Assessment Procedure used by the building regulations. The first 25% reduction was made in 2010, under the Labour government. Another 25% reduction was intended for 2013, but the Coalition government brought in a mere 6% reduction, and brought it in a year late, in 2014.
