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Improving Window Insulation

When thinking about insulation most people consider the loft and cavity walls, particularly as there may be grants available for doing this.  It is very important to do this and it pays for itself quickly by reducing your energy bills, but it does not stop there.  Benefits may also be gained from other aspects of home insulation that can also improve the appearance and functionality of your home, in addition to making it more energy efficient. 

The following article sets out our experience of trying to improve our energy efficiency by better insulating our windows.

We already have double-glazed windows that were installed during the early 1990’s, but these are nowhere near as energy saving as modern triple-glazed windows.  However, our windows still function and are uPVC, so we would be bringing forward a big waste disposal issue if we decided to replace them before they reached the end of their useful life.  It is also expensive to install replacement windows and, for people in conservation areas or for listed properties, there may be planning constraints on doing this.

Our house was built in the early 1970’s when large windows were fashionable and they give a lovely feeling of space and light, with a real connection to the garden, which we value.  They also give us useful heat from the sun (solar gain) through the patio doors in the morning and the front window in the late afternoon.  We do not want to lose those benefits but, when it is dark or cold, we want to keep in the heat and reduce our energy bills.  A particular problem is our landing window on the cold, north side of the house that never gets any direct sun.  Conversely, our patio doors can give us too much heat and glare on summer mornings as they are east-facing, but then they lose heat once the sun has gone.

Our solution was to make use of blinds and curtains to reduce heat losses from our windows, as well as to control light and solar gain.

Our front living room window looks directly onto our seasonally changing garden, but it is not overlooked from the street.  It faces west, providing warm afternoon light but can cause glare once the sun gets lower in the sky.  We wanted something that would allow us to control the light, without losing the garden aspect, and which would provide additional insulation at night.  After considering a number of options we chose white painted FSC wood Venetian blinds.  These will lighten the room and give us the ability to direct the sunlight to maximum effect, either to reduce glare or to increase light by reflecting it into the room, without losing our connection with the garden.  Fitting the blind within the window recess provides a useful insulating wooden layer when the blind is closed, even though it is not sealed at the sides.  To further increase the insulation we will add curtains at the front of the recess, covering the window area and resting just above the radiator.  Currently we are investigating thermal linings and an interlining for the curtain, which should be good for insulating the window area, so long as they do not make the curtains too bulky for the space when opened.  Although the main purpose of interlining is to make the curtain look thicker and fuller (it consists of a thin layer of cotton wool – like material sandwiched between the face fabric and the lining) it also adds a little extra to the heat retention properties of the curtains.  If this was for a bedroom then we might choose a blackout lining with interlining option so as to exclude any external light, such as street lights or early dawn sunshine.  In fact, as the curtains will only be closed on winter nights, we have chosen a velvet curtain with blackout lining.

For the patio doors we want to make the most of the times in the mornings when the sun floods into the dining area.  However, in summer it can be uncomfortable sitting at the table in the full glare and heat of the sun, so we need to be able to lower a blind to reduce the solar gain.  But when direct sunlight has gone and during darkness, the patio doors can represent a significant heat loss and so we need to insulate the whole door area.  The perfect option for us was a Luxaflex Duette 32mm blind fixed within the recess and close to the window.  We decided to retain the existing velvet, lined curtains so that during the colder months they can be closed to further supplement the insulation effect of the blind.  The Luxaflex Duette is a double-pleated blind, having two layers of material and an air-gap between, creating a honeycomb structure that acts as insulation, both reducing heat loss from windows in winter and reducing solar gain in summer.  The Duo Tone fabric has white window facing fabric, which performs best in reflecting the sun, whilst the room remains light. 

We have a north-facing landing window that is quite large considering it is the side of the house that gets no exposure to the sun and is close to mature trees.  Large windows on the north side of the building lose more heat than other windows so this is a prime area for energy efficiency measures.  We wanted to keep the window because it lights the landing and we like to watch wildlife in the trees just outside, but it does feel cold in the autumn/winter months and is clearly losing us heat.  We decided to try a new product, the Luxaflex Architella 64mm blind.  This also has a pleated honeycomb structure, but has four layers of material arranged like a honeycomb inside a honeycomb, creating three air pockets across the blind.  It is claimed to double a standard double-glazed window’s insulating properties, thus producing significant energy savings.  Having seen the data provided by Hunter Douglas (Luxaflex parent company) we are keen to experience this effect for ourselves and, if possible, monitor its performance in our own house.

For more information and to see videos about these blinds visit www.blind-inspiration.com.  This is a family business that is local to us and was chosen to supply and fit our blinds on the basis of their experience and product knowledge, as well as for their interest in our project and willingness to provide us with access to further data to assess the blinds.

We hope to post further updates on the energy savings achieved after our blinds are fitted, so please visit this site again from January 2010.