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Open vs Closed Panel Timber Frames: What's The Difference & Which Do I Need?
If you’re comparing timber frame systems, one of the first decisions you’ll come across is whether to use an open or closed panel.
In my experience, the confusion around open and closed timber-frame panels usually comes from the way they’re explained.
The basic difference is actually quite simple: with an open panel, more of the work is left to complete on site; with a closed panel, we complete more of the wall build-up in the factory before it reaches you.”
That difference affects far more than the panel itself. It influences the amount of labour required on site, how quickly the frame can be completed, and how much control we have over the quality of the insulation.
So, without further ado, let’s look at how each system works and when I’d choose one over the other.
What Is an Open Panel Timber Frame?
At Ty Eco, our open-panel option uses our standard 140mm timber stud system with external OSB sheathing, but leaves the internal side of the panel open so that insulation and the remaining wall build-up can be completed on site.
It’s the most basic form of panelised timber frame that we supply, and it can suit projects where the builder specifically wants greater control over that work once the frame has been erected.
We can still manufacture open panels, but I see far less demand for them than I used to. More clients are recognising that if we can complete insulation and more of the panel build-up in controlled factory conditions, there is often little advantage in taking that same work back onto a building site.
What Is a Closed Panel Timber Frame?
A closed panel takes the same basic timber-frame principle further by completing more of the wall build-up before the panel leaves our factory.
With our standard 140mm closed panel, we install the insulation in the factory, incorporate the vapour control layer internally and apply the external OSB sheathing and breather membrane as part of the panel build-up.
For me, this is where closed panels really start to make sense.
We can install the insulation in controlled factory conditions rather than asking somebody to complete the same work outdoors on a live building site. That gives us much greater control over the finished panel and reduces the amount of work still waiting for the site team.
Does a Closed Panel Mean Passive House?
You can have our standard 140mm timber-frame system as either an open or closed panel.
Our ADRA system sits above that as our higher-performance panel for projects targeting Passive House levels of performance, and ADRA is manufactured as a closed-panel system.
So I wouldn’t choose between open and closed panels simply by asking whether you want a Passive House.
They are really two separate decisions:
What level of building performance are you trying to achieve?
How much of the construction work do you want completed in the factory before the frame arrives on site?
Open vs Closed Panel Timber Frame - Key Differences
Feature
Open 140mm Panel
Closed 140mm Panel
Factory completion
More of the wall build-up is left for site
More of the wall build-up is completed in the factory
Insulation
Installed on site
Installed in the factory
VCL and membranes
Installed on site
VCL & Breather Membrane are pre-applied in the factory, with only panel-to-panel connections requiring taping
Site labour
More work remains after erection
Less work remains after erection
Quality control
Greater reliance on site installation
Generally a superior quality of installation, due to most of it happening in a more easily controlled factory environment.
Best suited to
Projects that specifically want more work completed by the site team
Projects prioritising speed, consistency and reduced work on site
When Should I Use Open Panels?
Open panels were most common in the early days of timber frame construction, but it’s now largely moved towards closed panels.
I’d normally look at an open panel where the client or contractor has a specific reason for wanting to complete more of the wall build-up themselves on site.
That might be because they already have the labour and expertise available, or because their construction programme has been designed around completing that work traditionally.
We still manufacture open 140mm panels, but they’re not the option I would automatically recommend simply because the initial panel price may appear lower before you consider the added-value involved with a closed panel system.
How Does The Cost Stack Up?
Open panels will usually have a lower factory cost because more work is left to complete on site. Closed panels involve more work in the factory, but can reduce the labour and time needed once the frame arrives.
I’d compare the total installed cost, not just the panel price.
For me, that’s the key difference: with a closed panel, we’re moving more of the work from site into the factory, where we have greater control over the finished product.
For a wider cost comparison, read our guide on whether a timber frame house is cheaper to build.
Cost Factor
Open Panel
Closed Panel
Factory cost
Lower
Higher
Work left on site
More
Less
Site labour
More required
Significantly Reduced
Best suited to
Builders wanting more site flexibility
Projects prioritising speed and factory-controlled quality
So, Which One Is Right For Me?
For most projects, I’d choose a closed panel because it gives us greater control over insulation quality and reduces the work required on site.
I’d choose an open panel where the builder has a clear reason for completing more of the wall build-up themselves.
If you’re aiming for Passive House performance, I’d then look at whether our ADRA system is the better fit.
Send us your drawings and we can help you compare the options before you commit!
