Brr… it’s cold outside!

Paul Johnston
I want a Garden Office
5 min readOct 15, 2021


Previous post: So… that’s a glorified shed

In this little saga, I had come up with some rules as to why I wanted a garden office:

  1. I needed a space to do actual work. Simply put, a desk and a computer, and quiet where I could have video calls as well.
  2. I needed a space that would work in summer, winter and in the evenings, so a “glorified shed” without good insulation or heating would not be good, so I needed to consider that
  3. I needed the space to work in the garden and be usable by others. It wasn’t just going to be “my space” but might have to be repurposed as a garden space. The garden isn’t big. This is a big consideration.
  4. As environmentally friendly as possible. I’m not just going to concrete (bad) over a bit of the garden and dump a plastic filled monstrosity on it, however “aesthetically pleasing” it might look. Let’s see if it’s possible to make it good for the planet and work for us too.

Given all of that the first thing that really mattered was how to make sure that the garden office was both quiet and well insulated while also being able to stay cool in the summer with the sun out.

There is a lot of information about this when it comes to buildings but not when it comes to garden rooms. The assumption is that your garden room is largely a summer room only, and you really shouldn’t need it in the winter, or if you do, then here’s a heater.

When you start to look at garden offices, and garden rooms, what you find is that while they may say “insulated” what they mean is that the walls and ceiling may have insulation, but it is not unusual to find that the floor does not. When the floor does not have insulation, you find that your feet get cold, and the room does not retain heat as well (even though hot air rises, it will still escape). Also, it depends on how good the insulation actually is.

Insulation and “R-values” and “U-values”

When talking insulation you want to know about the R-value and/or the U-value. Essentially the R-value is how much heat is lost, or how “resistive” whatever material you have is to losing heat. See for more info. The U-value is the inverse.

Also, most materials are rated against “approved installation”. If you install it badly, the R-value gets worse. Also, doubling the thickness tends to double the R-value (not always, but close).

To get an idea of how different materials can provide wildly different R-values, there is a table on wikipedia: Most of it is below. What you can see is that manufactured insulation materials have a significant advantage over what might be considered “good” insulation materials.

Example R-values for some materials

Garden offices are not well insulated

When you start to look into the insulation of a lot of “garden rooms” and “garden offices” many of them are not well insulated. They might have some insulation, but it will be the same kind of insulation you might get in a loft space, or a bit better, and that’s not bad, but it won’t be great.

Not only that, but it will often be added into the “gaps” in a wooden frame.

I took a still from this youtube video:

100mm floor insulation

Now, this is pretty good as it goes and it’s way better than not having anything. But it’s bespoke. Someone has to build it that way. To install it you have to put in expanding foam around each edge as well to install each insulation board to ensure it’s air tight. The downside is that you’ve got insulation + wood. Wood is pretty good insulation, but it’s not perfect. The upshot is you’ve probably got an R-value of between 3 and 4 at this point, which isn’t bad, but could be better if the panels were just laid on top (which you wouldn’t do, because they aren’t meant for working with like that).

And they insulated the inside the same way but with 50mm foam not 100mm foam, which… reduces the R-value. They put 100mm on the roof which is good (heat rises).

Wall insulation

Now, in some ways, I’m not criticising. This is actually a good build in comparison to many I’ve seen. It has insulation (and there is also sound proofing which would add some insulation too). But the problem is that this is very bespoke and very time and labour intensive.

In other words, this isn’t your normal “I need a garden office” solution. This is your bespoke “build me exactly what I need” solution.

SIPs panels

So I start talking to people and find out about SIPs panels:

Structural Insulated Panels

Most people outside of the construction industry (or compulsive viewers of TV shows where someone with too much money does a self build somewhere ridiculous) wouldn’t have heard about these too often.

They are a sandwich of two OSB boards, with some form of insulation (usually polystyrene) between them. They are strong enough to be used as walls for houses, and they have inherent insulating properties.

You can literally build houses with them. Just search YouTube for “SIPs house time lapse”

This felt like a good thing to build a garden room out of. If I could find a supplier.

And there are a few companies out there who do garden offices using SIPs.


But… they’re quite a bit more expensive than the glorified sheds, or the lower quality insulation solutions.

Unless you’re prepared to “self build”.

Um… right.

Next post: An… attempt to be based



Paul Johnston
I want a Garden Office

ServerlessDays CoFounder (Jeff), ex AWS Serverless Snr DA, experienced CTO/Interim, Startups, Entrepreneur, Techie, Geek and Christian