The high cost of getting specification wrong
Get the window and door specification wrong on a new build scheme and it doesn’t stay hidden for long. It turns up on the snagging list. It turns up in a failed Part L submission. It turns up in a phone call from a site manager three weeks before handover, asking why forty plots are waiting on one missing profile.
Windows and doors sit at the point where building regulations, buyer expectations and programme delivery all meet. Specify well and nobody notices. Specify badly and everybody does. Here’s what developers and specifiers need to get right when choosing new build windows and doors, and what actually separates a supply partner worth keeping from one you’ll be replacing on the next scheme.
As a trusted trade manufacturer, supplier, and installer, Shelforce brings decades of proven expertise to every project. Working closely with major contractors, we understand the tight schedules, complex logistics, and strict compliance demands of modern developments, and we know how to keep your builds running smoothly.
Part L and Part Q: the two documents that decide your spec
Two parts of the Building Regulations do most of the work in deciding what a new build window or door needs to be.
- Part L governs energy efficiency and heat loss through the building fabric. Under the current Part L 2021 standard, new dwelling windows must meet a limiting U-value of 1.4 W/m²K, tightening to 1.2 W/m²K where more than 60% of a wall is glazed, alongside a minimum Window Energy Rating of Band B. The Future Homes Standard, published in March 2026, raises the bar further: new homes will need to produce at least 75% lower carbon emissions than the 2013 baseline, with notional window U-values around 1.2 W/m²K and triple glazing (typically 0.8–1.0 W/m²K) becoming a much more common specification. It applies to new non-high-risk buildings from 24 March 2027, with transitional arrangements for schemes already committed to Part L 2021. If you’re specifying now, design to the incoming standard, not the outgoing one.
- Part Q covers security. Windows and doors in new dwellings must be manufactured to a design tested against PAS 24:2021, covering resistance to forced entry through the frame, glazing and locking mechanism, not just the glass itself. It’s a design and testing requirement, so it needs confirming at specification stage, not retrofitted after installation.
Between the two, a handful of key factors decide whether a product passes: the U-value and g-value (solar heat gain coefficient) of the panes of glass, the thermal performance of the window frames themselves, the number of seals reducing heat transfer at the frame junction, and documented PAS 24 test evidence for the whole unit. Miss any one of these on paper and the whole plot fails inspection, regardless of how the finished window looks or performs on site.
Managing volume supply across dozens (or hundreds) of plots
Compliance is only half the challenge. The other half is delivering hundreds of identical units, on time, to a build programme that rarely stays still.
A single missed delivery on a 200-plot scheme doesn’t just delay one house. It delays every trade booked in behind the glazing team, and it’s the kind of hold-up that shows up in the client’s cost report. Managing that risk comes down to a few practical things: manufacturing capacity that can flex with programme changes, consistent lead times you can actually plan around, and a single point of contact who understands construction sequencing rather than treating every order as a one-off retail enquiry.
Material choices matter here too. uPVC windows remain the standard specification for the vast majority of UK new build because they combine low unit cost, minimal maintenance and reliable thermal performance across large volumes. Aluminium is typically reserved for larger glazed areas, patio doors and bi-fold doors where slimmer frames and structural strength are the priority. Knowing which to specify where, and having both available from one supplier, keeps the palette consistent across a site without juggling multiple manufacturers.
What separates a capable supply partner from a basic supplier
Choosing a manufacturing partner involves looking past basic price tags to evaluate true reliability and capability. A basic supplier delivers products to a gate and leaves the logistics to you. A capable supply partner acts as an extension of your project team.
The best partners provide clear technical guidance, reliable delivery windows, and robust products that minimise callbacks. Clear communication and proven manufacturing capacity prevent costly downtime, ensuring that every window frame fits correctly and performs as expected from day one.
Why Shelforce is the smart choice for your programme
Choosing Shelforce means partnering with a manufacturer that delivers much more than standard fenestration products. Honoured with the prestigious King’s Award for Enterprise in Promoting Opportunity, we combine commercial excellence with an inclusive employment model where 75% of our workforce lives with a disability
We work closely with contractors and housing associations across the Midlands, delivering high-performance products backed by decades of industry expertise. From boosting a property’s exterior kerb appeal to guaranteeing long-term durability, our manufacturing approach brings unmatched reliability to your supply chain.
Let’s discuss your upcoming project requirements
Ready to secure a dependable manufacturing partner for your next development? Get in touch with the Shelforce team today to discuss your specifications or request a detailed quotation.
- Online contact form: Shelforce Contact Us
- Telephone: 0121 603 5262
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