mouldy window frame

What Is the Difference Between Wet Rot and Dry Rot?

Rot is bad news. When this happens to the structural elements of your house, it can spell disaster! But even if it’s just the superficial parts of a door or window that are affected, rot can be a real pain.

You might even have heard that there are different kinds of rot, which manifest in different ways. Don’t worry, we’re not going to delve into the biochemistry here (interesting though it may be); instead, we’re going to look at the practical consequences of rot, and how to avoid them.

What is Wet Rot?

Certain sorts of microscopic fungus will multiply when the moisture levels get high enough. As they spread, they’ll need to eat. And what they eat is the timber in your home. There are many species of fungus that do this, but the most common cause wet rot: they’ll discolour your timber and cause it to fall to bits.

What is Dry Rot?

Certain sorts of fungus have a distinctly different effect on the wood they’re chewing through. Timber infested with dry rot will become brown and crumbly, sometimes so much so that it can be broken into powder between your fingers. Despite what you might assume, dry rot needs a certain amount of moisture to survive – typically around 20%.

Dry rot is rarer than wet rot, though considerably more serious. It will spread away from the source of the damp rather than staying close to it, meaning it could quite literally bring the house down. Don’t delay in treating it!

How to Fix Window Rot

Once you’ve identified the sort of rot you’re dealing with, you can move onto fixing it.

How Do You Fix Wet Rot?

The affected area will need to be stripped out and repaired, blending any replacement timber in with the existing stuff. Of course, this will only prove effective in the long term if the source of the moisture is dealt with.

How Do You Fix Dry Rot?

Timber affected by dry rot should be treated with a suitable fungicide and wood preservative. Badly affected or warped timber should be replaced with a pre-treated substitute. This will lessen the chance of the timber being infected again. Given the serious consequences of a dry-rot infestation running out of control, this is something you’ll want to bring in specialist help for.

How Do You Stop Window Rot?

Prevention, as they say, is better than cure. And so, it’s best to stop rot from occurring before it starts. It’s a good idea to control the ambient moisture level around your timber, and to get damp looked at before it spreads. But if you’re dealing with timber on the outside of your house, such as in a window, this might not be an option. In this instance, look for a lengthy guarantee against rot and fungus when you’re buying the window. Our timber windows ship with a forty-year guarantee against rot and fungus, giving you peace of mind from the moment you install.

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Do Glass Windows Protect against UV Rays?

Ultraviolet radiation refers to light that is at a higher frequency on the electromagnetic spectrum than the light we can see. It’s notorious for being bad for your skin and eyesight, for being associated with various sorts of cancer, and for causing sunburn.

If you’re shopping for a new window, these are all things which should concern you. Does ultraviolet light pass through glass in the same way that visible light does? And, perhaps more importantly, can you get sunburnt from sitting beside the window? These are the questions we’ll be tackling in this article.

Do UV Rays Go Through Glass?

The answer is a little bit complicated. Not only are there different sorts of glass with different properties, but there are different sorts of UV light, too.

Shorter-wavelength UV-B rays are easily excluded, but longer-wavelength UV-A rays can easily pass through a normal glass window.

If you’re wondering, there is such a thing as UV-C – but these wavelengths tend to get blocked by the atmosphere before they even strike the surface of the planet. So, that’s one less thing to worry about!

Can You Burn Through Windows?

Common glass windows in your car, home, office and in our range will block almost all UV rays that reach the Earth. Glass does struggle with UV-A rays as mentioned before, so whilst you may not feel burning, the UV-A rays can still cause damage to your skin. However, in the UK, you’re going to have to be sat by a sunny window for a long time for that to happen. If you are going to be by a window on a sunny day for hours and your skin is quite sensitive, then some sun block won’t hurt.

Sunburn, moreover, is just one type of skin damage that can result from excess UV exposure; certain sorts of people will be vulnerable to increased freckling and photodermatitis (a skin condition exacerbated by exposure to light).

For an average person in the UK, you really don’t have to worry about burning through your windows on a sunny day. But UV radiation and its effects on the skin aren’t to be ignored. Take care in sunny conditions and always err on the side of caution. Remember also, that you can get sunburnt on a cloudy day.

Of course, some of us deliberately seek out the sun in pursuit of a healthy-looking tan. We’ve covered how windows can contribute to tanning in a previous blog, so be sure to check that out.

Another factor we haven’t considered is that the UK doesn’t receive all that much sunlight – so unless you’re sitting in a conservatory for hours on the south side of a building, you’re unlikely to suffer much. While obviously being true, this fact doesn’t stop UV rays from being damaging. If you’re fortunate enough to work in a greenhouse all day (or unfortunate enough to work at a computer besides a sun-facing window) then it’s important that you aren’t blasé about the damage the sun can inflict. Draw the blinds (or apply some sun lotion) and give yourself peace of mind!

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Man installing a window

When to Replace your Windows

A good set of windows will last for decades, providing consistent draught exclusion and insulation throughout that lifespan. But as with all structures of this sort, even the most stringently manufactured window will one day begin to break down. To ensure that your home enjoys the best possible security and energy-efficiency, it’s vital that you invest in a replacement set when your windows reach the end of their lifespan.

Signs Your Windows Need Replacing

But exactly how do we know when it’s time to call time on that trusty double-glazed window set? There are a few common signs which can help clue us in. We’ve touched upon the signs that double glazing is failing in a previous blog, but we’ll briefly recap them here:

Physical Damage

Begin by examining the window itself. Is it in good shape? Are the seals still intact? Does it open smoothly? If your window has been cracked, then it might be possible to get it repaired. However, if the window was already a little long in the tooth, it will probably make more sense to look for a replacement instead.


In the case of uPVC windows, you’re looking for a yellowing which occurs when the plastic is exposed to direct sunlight. Over the years, all of that UV can take its toll on certain older sorts of uPVC. Happily, modern stuff can withstand a great deal more before it starts to discolour.

If you’re replacing a timber window, then you’re looking for signs of warping and rotting. You might be able to address this with a little bit of preventative maintenance: sanding and refinishing can work wonders. Eventually, however, you’re going to have to replace.


While condensation on the inside of a window during winter indicates that the panel is performing well, the same isn’t true of condensation that forms between the panels of your double glazing. This space is built to be sealed. If any moisture has gotten inside, then that means that the seal has failed, and all of the heat-preserving gas has leaked out.  This means the energy-retention of your window will have plunged.

Can You Replace Windows in the Winter?

A necessary evil when it comes to window replacement is that you’ll need to remove the old set before installing the new one. As such, there will be a short period when your home is open to the elements. If this period occurs during cold weather, then your house will become very cold, very quickly. As such, many installers will recommend against replacing during winter.

However, if you plan competently, there’s no reason that you can’t get your windows replaced at just about any time of year. We are, after all, only talking about a short interval where you won’t have any window at all. Just be sure to check the weather forecast on the day in question, and don’t be afraid to push things back if there’s a blizzard incoming.