SIP Explained

Q: What does SIP stand for?

SIP stands for Structurally Insulated Panel: a composite panel with OSB facings and a rigid insulation core, providing both structure and insulation.

Q: What U-values do SIPs achieve?

A 150 mm SIP panel is typically around 0.21 W/m²K. With internal insulated plasterboard, U-values improve to ~0.16 W/m²K. Additional layers are required to match CPS levels of 0.13–0.15 W/m²K.

Q: How do SIPs compare with CPS on build speed?

SIP shells can be erected in 5–7 days, but CPS reaches wind & weathertight faster as airtightness, vapour control and service cavities are factory-integrated. SIP requires more follow-on trades, extending the programme.

Q: Do SIPs need extra finishing layers?

Yes. SIP builds require vapour control foil, service battens and insulated plasterboard to match CPS performance, adding time and cost.

At a glance: SIPs (Structurally Insulated Panels) are factory-made panels consisting of two OSB facings bonded to a rigid insulation core. SIPs are strong, thermally efficient and faster than masonry or conventional timber frame — but compared with HebHomes’ CPS, SIPs require more follow-on trades (vapour control, service battens, insulated plasterboard) to achieve similar U-values. As a result, SIP builds take longer to complete and involve more layers on site.

Typical SIP wall panel: OSB facings + polyurethane insulation core (≈150–225 mm thick).
Standard 150 mm SIP ≈ 0.21 W/m²K; with extra internal insulation layers, ~0.16 W/m²K.
To match CPS (≈0.13–0.15 W/m²K), SIPs require additional insulated plasterboard internally.
Follow-on trades: vapour control layer (VC foil), service battens, internal insulation board.
On-site programme is typically longer than CPS due to extra finishing steps.

What are SIPs?

Structurally Insulated Panels (SIPs) consist of a rigid polyurethane insulation core bonded to two sheets of OSB. The panel acts as both structure and insulation. SIPs are manufactured by specialist suppliers (e.g., Hemsec) to HebHomes’ designs.

Performance & follow-on works

Thermal: Standard 150 mm SIP ≈ 0.21 W/m²K. With internal battens + insulated plasterboard, ~0.16 W/m²K. Extra layers are required to match CPS (0.13–0.15 W/m²K).
Airtightness: Panels are inherently airtight but joints must be sealed precisely; late service changes are more disruptive than in CPS.
Follow-on trades: VC foil, service battens, and insulated plasterboard are installed on site after erection — unlike CPS where these elements are factory-integrated.
Programme: SIP shell erection is rapid (5–7 days typical), but the additional trades extend the overall timeline compared to CPS.

SIP advantages vs traditional build

Stronger and more thermally efficient than masonry or standard timber frame.
Factory consistency reduces waste and speeds erection of the shell.
Allows design flexibility — panels can be cut to bespoke sizes.
Good acoustic performance; quieter internal environment than masonry/timber frame.

Limitations vs CPS

More follow-on trades: VC foil, battens and insulated plasterboard required on site.
Longer programme: SIP shells go up fast, but finishing stages extend timelines.
Lower base U-values: Requires additional layers to match CPS performance.
Service routing: Cutting into SIP panels risks compromising airtightness; CPS includes a built-in service cavity.

Common Questions

What does SIP stand for?

SIP stands for Structurally Insulated Panel — a composite panel with OSB facings and a rigid insulation core, providing structure and insulation in one element.

What U-values do SIPs achieve?

A 150 mm SIP panel is typically around 0.21 W/m²K. With internal insulated plasterboard, U-values improve to ~0.16 W/m²K. To match CPS levels (≈0.13–0.15 W/m²K), additional insulation layers are required.

How do SIPs compare with CPS on build speed?

Both systems allow a rapid shell erection (≈5–7 days). However, CPS reaches wind & weathertight faster because service cavities, vapour control and airtightness details are factory-integrated. SIP builds involve more follow-on trades, which extend the programme.

Are SIPs mortgageable?

Yes, provided they carry a recognised 10-year structural warranty (e.g., NHBC, Build-Zone, BuildCare). Lenders often ask for confirmation from suppliers like Hemsec.

Do SIPs need extra finishing layers?

Yes. A SIP shell requires a vapour control foil, service battens, and often insulated plasterboard internally to match CPS thermal performance. These add time and cost compared to CPS.

Are SIPs sustainable?

SIPs use less raw timber than standard timber frames and have lower operational energy demand. However, CPS often achieves better thermal bridging control and higher pre-manufactured value, reducing whole-life impacts further.