Why Choose a Closed Panel System?
At a glance
Our CPS (Closed Panel System) delivers the best overall balance of speed, performance and assurance:
- Fastest to watertight: factory-fitted membranes/service zone; fewer follow-on trades than SIP.
- Lower U-values: walls typically 0.13–0.15 W/m²K without insulated plasterboard.
- Greener insulation: hydrophobic blown recycled glass-wool (non-oil-based) vs SIP’s PUR/PIR.
- Assurance: BOPAS + BBA, 60-year durability guidance; fully mortgageable.
- Architecture: deeper wall cavity reduces cold bridging and improves proportions/spans.
- Cost: A larger crane is required than for SIPs, adding to erection costs and potentially making SIPs the better option for some remote or challenging sites.
System Comparison
U-values (walls)
CPS0.13–0.15 W/m²K as standard; no insulated PB required.
SIP~0.16–0.21 W/m²K; often needs insulated plasterboard to match CPS.
Timber frameTypically 0.18–0.22 W/m²K unless upgraded.
MasonryOften 0.25+ W/m²K unless thick, costly cavities used.
Speed to watertight
CPSFastest — factory membranes/service zone; minimal follow-on trades.
SIPFast shell (5–7 days) but more internal follow-on trades before true weathertightness.
Timber frameSlower — open panels require site membranes, insulation, service battens.
MasonrySlowest — weather-dependent, long programmes.
Accreditation & warranty
CPSBOPAS + BBA, 60-year durability guidance; lender-friendly.
SIPBBA typical; BOPAS varies by supplier; lenders can be cautious.
Timber frameAccepted with NHBC/equivalent warranty.
MasonryUniversally accepted; no inherent system warranty.
Insulation & sustainability
CPSRecycled glass-wool (mineral, non-oil-based), hydrophobic; deep cavity.
SIPPUR/PIR rigid foam (oil-based, higher embodied carbon).
Timber frameMineral wool fitted on site (quality varies).
MasonryMineral wool/cavity fill; risk of gaps/cold bridges.
Cold bridging
CPSMinimal — double-stud breaks thermal bridges.
SIPJoints/edges need tapes/VCL; bridging at interfaces.
Timber frameNotable around studs and junctions.
MasonryHigh through lintels/block-to-block paths.
Factory fitting
CPSExternal membrane pre-fitted; service void ready for 1st-fix.
SIPInternal VCL + service battens fitted on site.
Timber frameMost membranes/voids installed on site.
MasonryN/A — relies on site workmanship.
Follow-on trades
CPSFewer — quicker critical path to M&E first-fix.
SIPMore — VCL, service battens, insulated PB usually required.
Timber frameMore — insulation, membranes, service void done on site.
MasonryMost — wet trades throughout.
Architectural flexibility
CPSDeeper cavity enables better proportions and spans; excellent for large reveals.
SIPGood, but internal service zone often added later.
Timber frameFlexible but performance drops without thicker walls.
MasonryVery flexible; slower and heavier.
Programme & prelims
CPSShortest — faster to watertight reduces prelim costs.
SIPShort shell but longer follow-on period.
Timber frameLonger overall due to site works.
MasonryLongest; high prelims.
Mortgageability
CPSStrongest case with BOPAS/BBA + 10-year warranty.
SIPGenerally acceptable with 10-year warranty; varies by lender.
Timber frameAccepted with mainstream warranties.
Useful Next Steps
