Open vs closed panel timber frame.
Cost, PMV, programme and quality — compared honestly.
Two routes to the same frame — the difference is where the work happens.
An open-panel timber frame arrives as engineered structural panels; insulation, membranes and services are added on site. A closed panel arrives with insulation, membranes and often service zones or windows already factory-fitted. Same timber, different split between factory and site — and that split drives cost, programme, quality control and funding position.
Lowest package cost, most site flexibility.
Open panel is the UK's most established route and normally the lowest package price. Insulating and detailing on site suits projects with flexible programmes and conventional specs. The trade-offs: more site labour, more weather exposure, and airtightness that depends heavily on site workmanship.
More factory, less risk, higher PMV.
Closed panel moves insulation, airtightness layers and membranes into factory conditions: tighter quality control, faster weathertight, fewer site variables — and a higher Pre-Manufactured Value, which matters on Homes England-funded schemes with PMV thresholds. The package price is higher; the programme and risk savings claw much of it back.
The project decides, not the factory.
Programme pressure, performance target, site constraints, funding requirements and budget each push the decision one way or the other. Because we supply and erect both, our recommendation follows the project. High-performance targets with tight programmes lean closed; cost-led projects with flexible programmes lean open; many land between, with closed walls and open elements where they make sense.
Frequently asked questions.
Is closed panel more expensive than open panel?
The package price is higher, but more of the build is completed in factory conditions — site programme shortens and quality risk drops. On funded schemes the higher PMV can be decisive.
What is PMV?
Pre-Manufactured Value: the proportion of a home's cost delivered through manufacturing and offsite processes. Homes England-funded schemes typically require a minimum PMV — closed panel scores higher than open panel.
Which is faster on site?
Closed panel. Insulation, membranes and service zones arrive already fitted, so the site stage is shorter and less weather-dependent.
Not sure which to specify?
Send us your drawings — we deliver both, so you will get the honest answer, not the factory's answer.