How Much Do Curtains Help with Heat Retention?

If you’re looking to save money on your energy bills, then you should view your windows as a priority.  A significant amount of heat is lost through a home’s windows, but there’s an easy way to reduce that loss – curtains.

Why do curtains help with heat retention?

Curtains help with heat retention by limiting the flow of air between the warm and cold areas of a room.  Even double-glazed windows will afford heat with a chance to escape, but a set of heavy curtains will form a barrier that’ll limit the flow of air from the main room to the window.

While some air particles will be able to move through the gaps in a curtain, many of them will encounter resistance – just like wind blowing against a ship’s sail.

Even if the air immediately beside the window cools considerably, if it doesn’t have the opportunity to mix with the warm air in the rest of the room, you won’t notice – and neither will your energy bills.

What about letting sunlight in?

Of course, if we’re concerned about energy efficiency, then we shouldn’t just be concerned with heat escaping the room; we should also worry about the sunlight that might find its way in.  Heat from outside your property can limit the strain on your energy bills.  It’s of particular concern if the window in question is south-facing, as there will be more direct sunlight to allow into the house.  As a rule, you should open up your curtains as soon as the light strikes them for best effect.

What sort of curtains are most effective for heat retention?

According to researchers from the University of Salford, drawing your curtains at dusk can reduce heat loss by around 15-17%.   With blinds, the figure is a little lower at 13-14%, but the difference is enough to make closing them worth it.  These findings have been echoed in laboratories across the world, with the US department of energy putting the figure at around 10%. This can go up to 25% if you’d like to seal your curtains to your wall on either side with electrical tape.  While this might seem like an extreme measure, it’s one that might be worth considering in areas where the rear of the curtains is unlikely to be visible.

How much heat can curtains help retain?

By extension, heavier curtains are better at preventing heat exchange between the cold air around the window and the warm air in the rest of the room.  The thicker the curtains, generally speaking, the more effective they are as an insulator.  The best insulating curtains come with a lining attached to the rear, which is designed to limit airflow and noise transfer.  You might even consider a second pair of curtains, designed for exactly this purpose, which hang just behind the first pair.

sliding window

What Are Trickle Vents For (and do you need them?)

Over the past few decades, considerable advancements have been made in the art of draught-exclusion.  Modern windows are airtight, which is great – in terms of energy-efficiency.

Unfortunately, while we don’t want draughts to get into our home, an entirely air-tight interior is bad news for moisture and air quality levels.  After all, there’s no point in having an air-tight window if you can’t see out of it because it’s covered in condensation!

For this reason, window-manufacturers began to build little cold air vents in the frames of their windows, which allow a small amount of air to pass from one side of the window to the other.  These are known as trickle-vents.

window with trickle vent

Do you have to have trickle vents?

The short answer is – it depends.

It was once the case that building regulations stipulated a ‘no worse than existing’ clause for trickle vents. This basically meant that if you were replacing a window with a trickle vent, you’d need to bring in another window with a trickle vent.

This rule went pretty much unchallenged until 2006, when the Department for Communities and Local Government (they’re the people in charge of building regulations) decided that all new windows should come with trickle ventilation.  The fenestration industry, much of which still manufactures and sells trickle-free windows, was displeased. After some discussion, the rules changed. What was once considered mandatory is now merely advisable.

This means that homeowners have a little more freedom to make their own decisions about the sort of windows they’d like installed.  The company carrying out the installation is sure to have an opinion on the property’s ventilation requirements, and it’s usually best to follow their advice.

What size trickle vents do you need?

If you’re replacing windows with trickle vents, the ventilators should be “no smaller in geometric open area than the existing ventilators“.

If this isn’t known, “habitable rooms should have trickle ventilator of 5000mm2 equivalent area and wet rooms should have 2500mm2 equivalent area“.

What are the alternatives to trickle vents?

There’s a very simple alternative to fitting windows with trickle vents – opening a window. It’s a good idea to open all the windows in the house for a few minutes every day (yes – even in winter!) to allow moist air to escape, and dry air to replace it.

This is especially important in the bathroom and kitchen.

Can I fit trickle vents into my existing window?

If you’ve got a problem with condensation in an older window, it is sometimes possible to install a trickle vent.  That said, fitting a vent takes considerable time and skill. In many cases, the best solution would simply be to get the window replaced.

Looking for new windows for your home? Browse our sliding sash or casement windows or find out about our handmade bespoke windows.

Bird on a window ledge

Why Do Birds Fly into Windows (and how can you stop it?)

Many modern conveniences that benefit us are harmful to the animal kingdom, who can’t understand that roads are hazardous or anti-freeze is poisonous.  Windows are another common hazard – especially to birds.

Why do birds fly into windows?

There are three main causes of window collisions.  The first is probably the least harmful, and it comes about mostly during spring, thanks to territoriality.  A bird will perceive its own reflection as another bird, and attack.  Since birds rarely attack one another by simply ramming their rivals out of the sky, such attacks are unlikely to threaten the bird’s life.  They’ll simply be dazed and confused for a moment, before recovering and flying away.

The other two causes are more likely to result in serious harm, or even death.  During the day, a bird might spy a plant they quite like the look of in the window, or a reflection of one from the garden outside.  Flying towards it, they’ll smash into the glass.  Other collisions happen at night, when nocturnal birds will be drawn towards the light.  What draws them toward the light, however, is a matter of some debate.

How can we stop birds flying into windows?

Preventing birds from flying into a window is a simple matter of making that window seem impassable.  Placing opaque strips along the length of the window, so that a bird’s wingspan would be unable to squeeze through the gaps, will prevent most collisions.  Of course, placing masking tape, plastic strips, or other such things on the exterior of your window will alter the aesthetics of the building, so you’ll probably want to perform a risk assessment before proceeding.

Other options include mosquito screens, hung externally; tightly-strung netting that will literally cause birds to bounce away unharmed. Specially-manufactured anti-bird tape is another option. This will do the same job as masking tape , with less visual impact.

Drawing your curtains at night will naturally prevent nocturnal birds from being drawn in by the light in your home.  It’ll help keep your heating bills under control, too.  Finally, if you have a cat who can be persuaded to sit on the windowsill for large portions of the day, you might find that birds are dissuaded from coming near!

condensation on window

Why Is There Condensation Between My Window Panes?

A steamed-up window is quite a common sight in modern homes – particularly if it’s cold outside and you’ve got the heating cranked up.  As the airborne moisture comes into contact with a cold window pane it condenses. This is normal (although you may want to take steps to reduce the amount of moisture in your home). Condensation that forms between the panes, however, is evidence of something a great deal more concerning.

How does double glazing work?

Double glazing makes a significant difference to the energy-efficiency of a building.  By sandwiching a layer of air between two panes of glass, we can slow the transfer of heat from one side to the other considerably.  When an inert gas like argon or xenon is used inside the cavity, the flow of heat is reduced even further.

In order to deal with any moisture that might get trapped between the panes during sealing, window manufacturers would use silica balls; the sort that you find shipped alongside electronic equipment.  These balls act as a desiccant; they’ll absorb small amounts of moisture, and prevent condensation from forming.

So what does all this mean for windows in which condensation has formed?  Simply put, it means that the seal which safeguards the interior of the window has broken, and airborne moisture from outside has found its way in.  The more condensation inside the window, the greater the degree to which the seals have failed.  This doesn’t just, of course, mean that you’ll need to put up with more condensation blocking your view of the outside world; it also means that your window will be far less energy-efficient.

Do I need to replace the window?

If your window’s still under the manufacturer’s guarantee, you’ll want to get it replaced straight away.  The window has failed, and they’re obliged to correct it.

If your guarantee has expired, you have a decision to make.  A double-glazed window with a broken seal will still function better than a single-paned window, but it won’t be anywhere near as insulating as a window with an intact seal.  Repairing the seal is difficult and expensive. It requires an engineer to identify where the leak is, suck the gas from the window, and refill it.  If there are multiple tiny leaks spread across the edge of the glass, a repair would be near-impossible.

Ultimately, the window will need to be replaced.

Looking for new windows for your home? Browse our sliding sash or casement windows or find out about our handmade bespoke windows.