可以从网上买size正好的窗户，自己换吗? 换窗户容易吗？
标准尺寸的窗子不一定适合你的窗洞，B&Q也有卖的。
很多印巴人开了很多做窗子的小公司，你找一个上门量尺寸做吧，安装费一般80左右一个窗子，如果你的DIY能力不是特别强还是找人装吧。如果你在伦敦，西北偏北 达人 认识一个印巴人小公司。
很容易的，需要水平尺，电钻，螺丝，膨胀胶。每个窗户拧上8个螺丝校正，膨胀胶密封住缝隙就好了。
看美国的BLOG换窗户很容易的，但英国是有法规，似乎要有FENSA注册才可以换：
http://www.diydoctor.org.uk/projects/replacementregs.htm
Replacing windows and doors is not quite such a simple procedure as it was pre April 2002. Since then you must have approval from the Building Control department of your local council to say that the replacement has been done in accordance with the building regulations. These regulations apply in England and Wales.
This means one of two things. The installation has to be done by an individual or company who is registered under the FENSA registration scheme. A glazing company with FENSA registration will install the windows and doors and issue you with a certificate to prove that the work has been done in accordance with the regulations. You must also make sure, as you are potentially changing the external appearance of your home, that you do not need planning permission for your changes.
那就是法律不允许自己换了？
目前的building regulation要求换窗子有fensa证书，如果要买房子这个有点重要。
如果没有fensa证书需要local council 报告，现在换窗属于，比较麻烦，而且很多保险公司用fensa的认证。
fensa是一个行业认证证书，我没有看到有关building regulation明文指定只有这个公司的认定才能安装。如果成龙大哥有相关的资料，麻烦分享一下。
这是我从网上看到的一段文字：
I thought that replacing windows did not need Building Regulations consent?
For many years, it has not been necessary to apply for Building Regulations consent when replacing windows in existing dwellings unless a structural alteration was involved. This usually only occurred when the existing opening was being made wider (which made the installation of a new support lintel necessary), or where the windows were part of a structural bay. However, from the 1 April 2002, all owners replacing windows and doors require consent, and the new windows themselves will need to fully meet the requirements of the Building Regulations. So even if you are replacing only one window bought from a local DIY centre you still need to follow the guidance below.
It is important that householders obtain the necessary consent as solicitors will make specific checks for this when the property is sold.
What do I have to do?
You have a choice, you can either:
Use an installer registered under the FENSA scheme run by the Glass and Glazing Federation, in which case you do not need to make a Building Regulations application to the Council. Your installer should then ensure your windows comply fully with the Regulations and will supply you with a certificate confirming this when the installation is complete. You will also be offered the option of taking an insurance-backed guarantee. Please ensure that your installer is properly registered under the scheme before placing an order. You can check this and find more details of the scheme by visiting the FENSA website.
Make a Building Regulations application to your local authority, and in most cases the simplest way of doing this will be to submit a Building Notice. You should complete an Application for Building Regulations Approval form, ticking Building Notice at the top, and return it to your local authority together with the appropriate charge at least two working days before removing the old window(s).
If all is found to be satisfactory your local authority will approve the work and provide a completion certificate. This will involve a surveyor calling at your property to check the installation of the new windows.
如果DIY,你需要向local council 报告申请，买窗的时候一定要厂家的产品证书，上面的保温U-value 是council关心的主要参数