Condensation on windows is a pain but is it a problem & how to stop it?

凝结在窗户上是坏事吗?

It’s that time of year when condensation on windows becomes a pain,我们早上醒来，看不到外面，窗帘是湿的，窗户底部有水，更糟糕的是，它会影响窗户下面的墙壁，导致石膏板和家具发霉。

Condensation is bad news in multiple ways – it indicates where a home has weak spots orthermal bridgesin its insulated envelope, it points to problems in high humidity levels in the home – possibly coming from hidden problems in basements, crawlspaces, walls orventilation systems– and some things are certain when a home has condensation running down the windows:

• Condensation won't disappear on its own
• Condensation is potentially detrimental to health as it allows for mold and mildew growth
• Condensation can cause damage to homes and lead to costly renovations and repairs

So, the question is – what should we do about condensation? How do we fix and prevent condensation in our homes?

Condensation in homes – the basics

So what is condensation? Condensation in its purest form is caused when humidity in the air comes in contact with a cold surfaceand it condenses from a gas to a liquid again.
Where we notice it most in our homes is on windows, or on the sides of a nice chilled glass of chardonnay or a cold beer – with the exception that one denotes a pain in the butt, the other pleasure!

The reason we notice condensation most on glass is that it’s an impervious material – the water has nowhere to go so it sits there, waiting for us to wipe it off and running downwards until it does find a surface to soak into – which is unfortunately where the problems start to occur. Unless of course it's soaking into our t-shirt on a hot summer's day - but we're talking here about the miserable & cold kind that sits on the bottom of windows in winter and can even freeze up if we're really unlucky and thewood stovewent out overnight! (Which is what inspired Harold Orr to design the Saskatchewan Conservation House, which in 1977 acted as a laboratory for the development of many previously unheard of building techniques that are now standard on the best performing houses in the world.)

The other factor to consider, other than warming cold surfaces to mitigate condensation which is the traditional route to reducing condensation on windows, is that it can also happen when there's simply too much humidity in a home. As noticed most often in the colder months of the year when it meets the cold glass of bedroom windows, as cooling air becomes unable to hold as much moisture, it condenses.

所以，最简单地说，窗户上的凝结是相对温暖潮湿的空气遇到寒冷表面的结果——但这是一个浮动的比例。

To look at this in a scientific way, let's use some information fromthe Passive House Institute．他们的建议是，家里的表面最低温度为55华氏度(12.6摄氏度)，如果相对湿度为50%，包括窗户的表面温度，以防止局部窗户玻璃的相对湿度超过80%——这是导致窗户或窗框上凝结的原因，如果是单层或双层玻璃，特别是铝玻璃条。

What’s the problem with condensation?

Traditionally, most building experts will mention mold and mildew as the main problemscaused by condensation in homes – but first off, here’s a point to think about in connection with condensation on windows that we haven’t seen specifically mentioned anywhere.

As a key element ofPassive House,Net Zero Energy and high-performance homesis consistently making the most ofPassive Solar Gain, having a home where each day starts with fogged over windows is absolutely a huge detriment. A hidden effect of condensation on house windows is that once the sun does come up, which could and should be heating our high performance home’s interior in the colder months, instead the sun’s heat is being used up to evaporate the window condensation while also putting all that moisture back into the home interior and ultimately raising the humidity level. (Most folks don’t realize that evaporation is the biggest cause of heat loss in a swimming pool also).

所以这是一个问题，使冷凝成为一个问题，不必要地使用能源-当然，潮湿也是由冷凝引起的，我们的房子通常没有建造来抵御潮湿。即使是轻微的水损坏也会在石膏板上留下严重的污渍和损坏，而其他时候你需要完全清除受损的石膏板并更换它——特别是当它受到霉菌和霉菌的严重影响时——通常会在窗户周围或房间的角落里出现一团黑点。

当潮湿的空气接触到墙壁、窗户、镜子等较冷的表面时，就会发生冷凝，这通常是我们首先发现霉菌和发霉的地方——但我们也在衣柜和家具后面看到过这种情况，因为空气不能自由流通，所以石板墙不会变干。

Mold can grow on virtually any organic material as long as moisture and oxygen are present. There are molds that grow on:

• Wood
• Paper
• Carpet
• Food
• Insulation

Because mold eats or digests what it is growing on, it can damage a building and its furnishings. If left unchecked, mold eventually can cause structural damage to building materials, rotting wood, disintegrating drywall, costing the homeowner money for remedial work and potentially reducing a home’s value

If the humidity level in a home is above 60%, certain molds start to grow and flourish in under 12 hours – so if condensation is present, there’s almost certainly mold and that may become a big issue..

Condensation, humidity, mold and health

Exposure to damp and moldy environments may cause a variety of health effects, (or none at all). Put simply, some people are sensitive to molds. For these people, molds can cause nasal stuffiness, throat irritation, coughing or wheezing, eye irritation, or, in some cases, skin irritation. People with mold allergies may have more severe reactions and immune-compromised people and people with chronic lung illnesses, such as obstructive lung disease, may get serious infections in their lungs when they are exposed to mold. These people should stay away from areas that are likely to have mold – such as a home with high humidity.

In 2004 the Institute of Medicine (IOM) found there was sufficient evidence to link indoor exposure to mold with upper respiratory tract symptoms, cough, and wheeze in otherwise healthy people; with asthma symptoms in people with asthma; and with hypersensitivity pneumonitis in individuals susceptible to that immune-mediated condition. The IOM also found limited or suggestive evidence linking indoor mold exposure and respiratory illness in otherwise healthy children.

In addition, also in 2004, the IOM found sufficient evidence to link exposure to damp indoor environments in general to upper respiratory tract symptoms, cough, and wheeze in otherwise healthy people and with asthma symptoms in people with asthma. The IOM also found limited or suggestive evidence linking exposure to damp indoor environments in general to shortness of breath, to respiratory illness in otherwise healthy children and to potential development of asthma in susceptible individuals. In 2009, the World Health Organization issued additional guidance, the WHO Guidelines for Indoor Air Quality: Dampness and Mold .

Other recent studies have suggested a potential link of early mold exposure to development of asthma in some children, particularly among children who may be genetically susceptible to asthma development, and that selected interventions that improve housing conditions can reduce morbidity from asthma and respiratory allergies.

Before we all panic because we noticed some condensation in our homes, remember that eliminating all mold and mold spores indoors is virtually impossible, butcontrolling indoor moisture and humidity levels will control the growth of indoor mold– so this is the key.

Condensation is a symptom of other issues

Consider condensation as a symptom and not a cause of home humidity过于高,所以,如果有发生凝结在windows上,我们建议的第一步是得到一个湿度计或湿度表监控测试的相对湿度水平——因为具有讽刺意味的是更高的性能的家,与空气壁垒和更好的门窗,更多的机会将会有湿度的问题,除非它与自动机械通风系统的设计就像HRV的& ERV的(很多都没有)。

最初的湿度计被称为背带式湿度计，它由两个温度计和一个连接在链条上的把手组成。一种温度计是普通的，另一种在它的灯泡上有一个布灯芯，被称为湿球温度计。

但现在是电子时代，所以如果钱不是问题，有智能湿度计可以全年监测，并有最大和最小警报。我们发现其中一个更好的是150美元左右的临时棒，有5年保修，是美国制造的!如果预算不够的话，我们对ThermoPro TP50数字湿度计有很好的经验——像罗宋汤一样便宜，非常准确，大约10美元就可以完成这项工作。

在一周内、一天中的不同时间监测家里的湿度水平，我们敢打赌，相对湿度会超过60%。If so, then there are several things to do that will help:

• Limit the amount of humidity being produced in the home or entering it.
• Ventilate the home to remove excess moisture.
• Dehumidify the air in the home to bring the relative humidity below the 60%.
• Heat andinsulate homes evenlyto try to prevent cold spots that will provoke condensation.

The question remains, how do we do all those for the best, to help reduce the humidity level and reduce the chance of condensation?

How to reduce condensation in homes?

我们应该如何限制室内湿度和减少冷凝?Once we’ve identified that a home is over the recommended humidity level of 60%, we should firstly try to identify where this excess moisture is coming from. All living organisms give off humidity simply by existing, humans, animals, even plants – so is the home large or small in relation to the number of occupants? This might be the ideal time to turf those 20 something kids out of the house, citing that they are risking devaluing their inheritance and that it really is time they got a place they can call their own (and leave us in peace!) – Surprising how rarely Mom’s buy into this as a plan!

Interestingly, up to half of the high humidity solution is changing personal habits in the home:

• Showering-浴室是家里最潮湿的地方，像淋浴这样简单的事情会释放大量的湿气到空气中——天气越热，时间越长，释放的水蒸气就越多。So, to reduce this avoidable humidity source and save energy and water, always be sure to shower with a friend, failing that the dog, or otherwise - simply try to keep to a reasonable temperature and timespan – whilerunning the bathroom fan淋浴期间和淋浴后的15-20分钟，让外面的空气湿润。由于我们看到的浴室风扇安装不正确的数量——可能还需要在阁楼空间再次检查浴室风扇是否正确地向外部通风，连接处是否用管道正确地粘好了——因为向屋顶通风只会在屋顶产生冷凝、霉菌和木材腐烂的问题，而不是在家里本身。在洗澡或淋浴时，也要确保使用合适尺寸的浴垫，以避免浴室地板浸透。浴垫应该有助于吸收一些水分，有助于减少房间里的凝结，特别是如果它和最湿的毛巾一起放在烘干机里。
• Cooking and using a kettle or coffee maker– Kitchens are the second biggest source of home humidity, cooking, kettles and appliances all release steam, so be sure to use pan-lids when cooking to reduce moisture being created from the water boiling, to speed up the time it takes to heat pans, and have a cooker hood that’s set to extract and use it all the while cooking and for a little time after. Again, much as with bathroom fans, check ductwork for taped and sealed joins – and when buying a new cooker hood, buy a quiet one by preference and then it’s more likely to get used.
• Close kitchen & bathroom doors– As bathrooms and kitchens are the worst culprits for condensation. when cooking food, boiling the kettle or taking a shower, ensure that the kitchen or bathroom door is kept closed to prevent the moisture in the air from going into colder rooms which will cause condensation to form if it touches a cold surface.
• Laundry– Never, ever, EVER dry laundry inside on a rack or line when it’s cold outside – every load releases almost 5 pints of water into the air. If it won’t dry outside, then don’t attempt to dry it inside unless in an exterior-vented dryer. The second advantage is for interior air quality – as theartificial scents in laundry detergents and softeners will mostly dissipate outsideso we aren’t breathing them in. Once again, double check ducting for leaks.
• Unvented gas heaters, stovetops & ovens– When natural gas or propane and butane burns it releases water vapor and potentially carbon monoxide. None of these are good in homes or our lungs or bloodstreams, so either choose a different heat source where possible, likea nice wood burning stove, or if not then ventilate to get that all outside.
• Humid basements or crawlspaces– When a home is built on acrawlspaceor basement this can often be the cause of humidity in the home – even when the home is newer many areas building Code’s lockhumidity in finished basement walls for years, causing damp and moldissues. Manybasements were built with inadequate insulation, see here to find out how to improve itif so, orsee here for more information on insulating crawlspaces．To learnhow to prevent mold in basements, see here– orhow to prevent humidity and radon gas in crawlspaces see here．To learnhow to build a home on a slab-on-grade foundationwhich is our preferred option, see here.
• Those pre-Christmas home renovations– People often want to freshen up their homes in preparation for the holiday season, but if painting large areas of wall then all that has to dry, and this moisture goes straight into the interior air unless the space is well ventilated. Be sure tochoose zero VOC paints, or it's even easy tomake VOC free paint, find out how here并选择天气好的时候进行内部粉刷，这样窗户就可以大开，让这些化学物质和水蒸气在室外通风。
• Modern air conditioning systems- Believe it or not,AC systems can raise the levels of the humidity in homes．具体来说，我指的是那些据称将节省高达50%电费的新型号，因为它们工作速度更快，使用的能源更少。花更少的能源，因为他们更快和更快的冷却家的部分是正确的。然而，旧的空调机型必须运行更长时间才能达到所需的温度，往往因为它们运行的时间更长，就能更好地消除空气中的湿度。另一方面，由于新型号能够更快地达到所需的温度，因此无法消除空气中的湿度。甚至可能会有比打开它之前更多的相对湿度，因为较冷的空气没有能力保持水分。解决方案是确保任何“冬季”模式实际上是一个除湿器，如果运行在冬季模式，相对湿度测量更小-我们有一些惊喜!
• Careful selection of houseplants- If living in an area where the natural humidity is already high, having plants such as Ginger, Asplundia, Monstera, Ficus Benjamin, Areca palm, and Bamboo palm will only make humidity problems worse – choosing plants like Peace Lily, Boston Fern, Orchids, Spider Plant, Tillandsia, Cactus and English Ivy should help lower humidity andimprove internal air quality, but water sparingly and often for best effect.
• Check for water leaks!– Any pipes carrying water in the house, both delivery of hot and cold or heating and evacuation, should be checked for leaks and any leaks fixed promptly. All excess humidity in a home’s structure is best removed at the source – so also check gutters, downspouts, roof coverings and rainscreening for signs of leaks.
• Choose & fit high efficiency HRV or ERV units-随着现代住宅的气密性越来越强，根据房产所在的气候区域，安装带有热量或能量回收的机械通风系统也是一个好主意。Tolearn more about mechanical ventilation systems, see here– or to discoverhow to choose between an HRV or ERV unit, see here．如果在寒冷的气候中，在HRV或ERV装置上安装一个低水平的疏散管道也是一个好主意，而不是一个屋顶的通风口，因为它会冻结，很难检查和保持干净。
• Fit a high efficiency and appropriately sized dehumidifier– Once everything has been checked and sources of humidity in the home reduced as much as possible – if the relative humidity levels stay too high then there is always the possibility of running a dehumidifier or multiple dehumidifiers for each level of the home to bring the humidity levels down into the ideal range to avoid condensation, mold and mildew.

其他减少家庭凝结的想法

A key condensation point is windows, and the best way to keep on top of condensation around windows is to be on the lookout for any damage to the sealant around the window frame as this can allow water in – to learnhow to fit and seal windows properly, see here．

Also, if there is some condensation, try to wipe down windows and window sills promptly with a sponge that gets wrung out down the drain and rinsed in bleach, to ensure no excess moisture enters the property's air and open windows as often as possible on warmer days to allow air to circulate.

As rooms like bathrooms are optimum environments for high humidity causing condensation, getting into the habit of using a silicone squeegee on shower enclosures and tile after finishing a shower encourages water to drain away rather than it have to evaporate.

Condensation on unused bedroom windows may be noticed last, especially as it is a room not used very often. Signs to look out for with condensation around bedroom windows are; water on the windowsill, damage to window frames and it is also important that you don't ignore black mold on soft furnishings like curtains or cushions – we would always suggest keeping the heat turned up in the spare rooms of a house – it’s generally a false economy turning off the heat as they become a magnet for damp, mold and insect attack.

I’ve just realized, the condensation is between the glazing panels!

Condensation within double glazing typically suggests that there is a problem with the sealed unit在windows。这意味着窗户边缘密封的一个点已经失效，并允许水分进入，因为玻璃和框架之间的密封胶将不得不更新。寻求帮助when to change windows, see here- or for help in decidingwhich type of windows to choose, see here．

对于较旧或质量较差的部件，用于密封(窗户周围)的密封剂可能等级较低或随着时间的推移变得松散。如果镜框中的玻璃密封圈和玻璃珠变质，水分就会进入镜框。Allowing large amounts of water to settle in a window frame like this for a long period of time will eventually affect the ‘air gap’ seal surrounding the two panes of glass and if it’s a wooden frame it will cause it to rot.

Sometimes, uPVC frames will crack and allow water to gather. Another reason why you may see condensation in double glazing is because of a fault with the ‘spacer’ bar. Most double-glazed windows now feature a ‘spacer’ in between the two panes of glass and this is full of desiccant, a highly-absorptive material which sucks up any moisture in the ‘air gap’ void. In fact, you're as likely to get condensation on new windows as old windows, and new windows may even increase condensation, since they should reduce draughts in the home. That said, condensation on the inside of windows is something we should try to reduce, since it can damage window frames.

If there is even the slightest imperfection in the seal, this desiccant can quickly become saturated by any moist air or water which enters. When it cannot retain any more, the moisture then begins to appear as condensation between the panes of a multi pane window, most often noticed on a sunny day when it looks foggy.

If you have condensation in double-glazing, then it is a sign that the sealant has failed, and this usually means that it will have to be replaced or resealed. If the windows are old, then replacing the whole unit can be recommended so that the same problem does not occur again.

What other types of condensation can happen in homes?

Interstitial condensation creates structural damping and subsequent damage当潮湿的空气渗透到家里封闭的墙壁、屋顶或地板内的隐藏空间时，就会发生这种情况。当充满水分的空气到达处于露点温度的间隙结构(或简单地说，墙壁或屋顶空洞)内部的一层时，它会凝结成液态水，然后浸透木材、绝缘材料和石膏板。这通常是平面和大教堂屋顶的问题，但它也经常发生在框架墙，但不会被发现，直到为时已晚，因为无处不在的聚蒸汽屏障干墙和钉。

The moisture laden air can penetrate into hidden interstitial wall cavity from the exterior in warm outdoor temperatures and inside the building during cold outdoor temperatures. The resulting structural damage, along with mold and bacteria growth may occur without any visible surface indications until significant damage or extensive mold and bacteria growth has occurred. To find out more aboutthe difference between air and vapor barriers, see here．

This is why it’s so very important tocarefully seal air-barriers in homes, paying special attention to joins and breaks in the membranes – especially where secondary trades have passed after air-barriers were fitted - and by using specialist sealing tape that stays stuck down properly.

Last but not least – if you live in a cold climate area that is susceptible to condensation in homes and are choosing toilets for a home construction or renovation, by preference specifylow flow toiletsdesigned with an insulated water tank to avoid water damage or mold below the cistern caused by condensation and it sweating down the wall.

Now you've learnedall about condensation on windows in homes, why it happens & how to stop that wet winter-time condensation nuisance, read more below: Top tips for getting a home ready for winter Why solariums won't heat homes in a cold climate in winter What causes ice dams & how to fix them And see moreGreen Building Guides for Sustainable BuildingsonNorth America's favorite sustainable building advice website- EcoHome.net