The easiest way to insulate walls from the exterior in older homes

How to insulate house walls from the outside

Adding extra insulation to the exterior walls of an older home when renovating or remodelingis a great way ofimproving a home's walls thermal performanceand reducing energy use while reducing heating bills, carbon footprint and improving a building's comfort level. It may look easy to go buy some packs of rigid insulation panels down at the local hardware store and screw them to your walls, but unless you understand how your existing walls are built and how they "work" in terms of keeping moisture, heat and cold where they should be for durability, the insulation panels might not be the only things you're screwing up!

Adding insulation to the exterior of a home correctly starts with establishing what climate zone you are building in and how the existing wall is built to make sure you are not creating a condensation point at a dangerous place within the wall assembly, or preventing internal moisture from the occasional leak in the exterior skin from running away, so the wall structure can dry out.

Walls need to be built to meet their specific climate needs. All too often ‘the best wall assemblies’ migrate from their own climate to one where they do not belong, like puttinginterior vapor barriers on homes with aircon in hot humid regions, which simply should not be done if you want your house to last.Durable, healthy and sustainable homes need careful research and planning- as changing one element without considering how this changes the dynamics of the building envelope is a potential recipe for disaster.

The best pre-emptive strike against the possibility of a nightmare exterior wall renovation and insulation project is educating yourself - so you don’t get talked into the wrong wall system by a poorly-informed general contractor. Start by watching our ‘building science made easy’ video below.

What is the right amount of insulation for walls?

Determining your climate zone will help decide on an appropriate amount of wall insulation for your home, whether you are in a heating or a cooling climate. Next, compile a short list of the types of insulation that best suit you by determining what your biggest concerns are. Consider some of the following: Cost, durability, fire-resistance, insect-resistance, low GWP (global warming potential), made with recycled materials, made with natural materials, which ones are best for sound proofing, or for reducing off-gassing to protect indoor air quality.

See our page onchoosing the right building insulation for the right application

一旦您确定了想要安装在外墙上的保温材料的大致数量和您愿意使用的保温材料类型，那么您需要找到一种方法，以保持其r值或保温质量的方式将其安全地安装/应用到外墙上。

How to avoid thermal bridges when fixing exterior wall insulation in place

For insulation to work properly on exterior walls and have a long functional lifespan, the wall system needs to have all the appropriate components, including an air barrier, a vapor barrier /vapor control layer, well balanced insulation, and be attached in a way that doesn’t compromise the R value of the insulation. But you already know that from the building science video right? Didn’t think there would be a test so soon did you ??heh heh…

Here is a page onthermal bridges: what they are and how to break them in buildings

But for those not clicking their homework assignments, here’s a quick summary – metal is a conductor, and when you have metal that passes from one side of a wall to the other, you have a thermal bridge, which is a path for heat to leave your home, and money to leave your wallet. To those of you living in Toronto or New York in older homes, this also applies to the elegant brownstone rowhouses, townhouses, and tenements that were built over a hundred years ago from brick and stone - neither of which are known for their outstanding insulating properties either.

当然，我们都想在尽可能减少碳足迹的同时限制能源的使用(和损失)，所以在翻新和升级外墙时，要注意你固定任何隔热层的方式——因为在一个完美的外墙组件中，保温层应该是连续的，不受热桥的破坏。以下是一些提高老房子保温水平，成功贴合外墙保温的方法。

Larsen trusses with cellulose or batt insulation

A Larsen truss wall is one with engineered I-joists attached to the outside of a stud or brick wall, which then creates a cavity that can be filled with additional insulation. You can add batt insulation, dense pack cellulose, rigid insulation panels or spray foam if you choose (spray foam is our least favorite but it can be done so we mention it, though we always encourage readers tochoose spray foam with the safest blowing agents)

Larsen truss walls can be made in a variety of thicknesses, which is a really nice advantage to the design as it can be done in a way that has the best return on investment for any climate. Below is a photo of aPassive House using Larsen trusses on the exterior of the wall (see video), that will then be filled withdense-packed cellulose insulation.

回到热桥——木材确实起到了热桥的作用，但没有金属那么重要，而工程i型托梁，只有5/8英寸，木材的导电性不是一个大问题，而且越深就越不重要。

Fiberglass thermal spacers or "Cascadia Clips"

The purpose of fiberglass insulation fasteners is to attach the clip itself to the frame, which then supports and secures the insulationwith a material that has a low conductivity to avoid heat loss, fiberglass clips also provide a solid surface for fastening strapping (furring strips) and exterior cladding.

Cascadia Clips from Cascadia Windows in Vancouver are the biggest name in fiberglass thermal spacers you will find across Canada and the U.S. so the concept has in a way adopted the brand name, but there are others brands of wall insulation thermal spacers such as Armatherm Z Girt available, pictured below.

Also, if installing a final finish to exterior walls over additional wall insulation, see our page onhow to install exterior siding so walls can dry.

Attaching insulation with metal screws

Above are a couple of ways to attach exterior insulation and maintain the highest possible R value by breaking thermal bridges, but the reality is that most exterior insulation is going to be a few inches of rigid insulation boards screwed or nailed to a wall with strapping. It’s not perfect and it does reduce the overall performance of the wall, but it’s not the end of the world, so don’t panic if you’ve already done it or are planning on doing it, we’re just trying to outline best practices.

We built ourLEED V4 Platinum Edelweiss Houseusing rigid Rockwool or Roxul insulation panels attached with strapping and screws (which is in the building science video above), and what we did to break the thermal bridge was to do it in 2 layers of 4 inches of rigid Rockwool so there would not be a single screw passing through the wall assembly.

它在能源效率和耐用性方面做得很好，尽管这不是我们所说的最有效的时间利用，因为做两层而不是一层意味着双倍的工作。事后看来，我们不太可能重复这个过程，但这就是我们学习的方式!You can see the whole Edelweiss LEED Platinum v4 certified Demo House being built in ourYouTube green building video series.

我们喜欢的一种替代的“主流”系统是ThermalWall PH面板，用于在外墙上粘贴刚性外保温材料，避免热桥。它是一个刚性的EPS泡沫保温板，有不同的厚度，这本身并不是一个新的概念，但有趣的部分是如何简单和快速安装。它最初是Legalett发明的，作为一种有效的方法，可以将外墙总r值提高到被动屋标准，轻松地将符合标准规范的R-24墙提高到R-52高性能包围线。

就连《树抱者》杂志的劳埃德·奥尔特在审查该系统时也写道:"there are some serious advantages to foam that can make a TreeHugger think twice, especially when one is talking Passive House, where one needs a lot of insulation and avoiding thermal bridges is a very big deal....关于泡沫隔热材料，我确实经常口吐白沫，而且一直在推广替代品。但这个系统确实提供了一层连续有效的隔热层……屋顶。它也会非常密封。It is such a simple system that makes a very good case for the stuff" which we agree with.

面板内嵌有镀锌金属轨道，当“快速轨道”被拆除时，金属轨道露出来。从那里，你可以把它螺丝到一个螺柱墙或进入砖石，然后你更换snap轨道和固定你的外部捆扎到相同的金属轨道。

这里的优点很多——面板厚度在4.5英寸到8英寸之间，外部绝缘是连续的，它们可以用4到6英寸长的6英寸10号螺钉连接。有一个将面板连接到墙壁上的中心螺钉和一个将外部毛条连接到轨道上的单独螺钉可以打破热桥。另一个好处是，这种长度的螺钉仍然是相当便宜的。根据经验，超过6英寸长，就需要1 / 4英寸直径的桁架头螺钉，它们开始变得非常昂贵——当隔热大型外墙区域开始增加成本时。

We realize that the mere mention of any kind of "Styrofoam" or foam insulation (ThermalWall PH is made with EPS / Expanded polystyrene) can upset the sensibilities of hard-core environmentalists, but it is worth keeping in mind that EPS insulation panels are mostly made of air, it is recyclable, the plastic content is a petroleum byproduct rather than primary material and it could be plant-based if it weren't for cost and the carbon footprint of doing so, and it works well when you use it for the right applications. It’s not "perfect", but then what in the building industry is? We've found that EPS's reputation as somewhat of an environmental "no-go area" is often based on a misunderstanding of what it is, and isn't, so we'd recommend remaining open-minded until you've got all the facts.To get a quote for ThermalWall rigid foam insulation panels, see here.

Even the greenest natural home insulation products have a carbon footprint of some kind, for example a strawbale house orstraw insulated SIPS panelshas diesel fuel in its history from fertilizing, irrigation, harvesting and transportation. And a lifecycle analysis of EPS (expanded polystyrene) insulation is not nearly as a bad as its reputation in some quarters of the green building industry would have us believe - but then a lot of the problem is it's usually thought of as Styrofoam in North America - which it may surprise you to learn it most definitely isn't. Just putting that out there, but we always welcome (friendly) dissenting voices and discussions in the comments section below!

The risks of condensation when insulating walls

The most important thing to remember when insulating exterior walls during renovations, is to be sure not to trap moisture between two vapor barriers. If a home already has a vapor retarder or vapor barrier, it’s important not to add another vapor-impermeable layer on the opposite side of the wall that could trap moisture in the middle along with organic materials such as insulation or wood framing members.

Some rigid insulation boards have integrated air barriers, some have vapor barriers, some have both and some have none. Some insulation panels (like EPS, XPS and polyiso) can act as a vapor barrier, which can be a good thing or sometimes a bad thing, so be careful!

This is why insulating exterior walls can sometimes go terribly wrong when "poor" insulation products are chosen for any given application. Don't just walk into a building supply store and pick the cheapest rigid insulation panel, that could be a disasterously expensive decision. This page will help explain:

The differences between Polyiso, EPS & XPS & Styrofoam

This is why deciding on a wall assembly for renovations has to be considered carefully to ensure that walls are able to dry out. Be sure to either have your wall assembly designed by a professional, but better still, get an understanding of the science behind it yourself, that way you will be able to spot anything that seems fishy with enough time to change it. Check out some of the links below, and if you have any questions that aren’t answered theylook in our discussion forum and maybe ask a question of your own here.

Now you know more abouthow to insulate house walls from the outsideand the pitfalls to avoid... Find more pagesabouthow to build energy efficient and durable walls here: Choosing a house wrap, which is best? How to choose between OSB and Plywood sheathing for Walls The difference between air barriers and vapor barriers How to install siding so walls can dry How to install windows properly in high-performance walls Find more about green home construction inthe EcoHomeGreen Building Guide pages