Wates Construction appointed Build Energy to provide specialist technical consultancy on the new houseblock expansion at HMP Wayland, a Category C training prison near Griston in Norfolk. The project forms part of the Ministry of Justice’s Accelerated Houseblocks Delivery Programme, which increases prison capacity through standardised, modern construction.
Our scope covers two specialist services: daylighting modelling and air tightness consultancy. Both directly support the project’s BREEAM Excellent target and the building’s long-term environmental performance.
About the Project
HMP Wayland is a working Category C training prison in Norfolk. The expansion will deliver 247 additional prison places within a new four-storey houseblock. The wider site development adds a 1,200-capacity kitchen, further education spaces, and industrial workshops. An all-weather sports pitch and site-wide infrastructure upgrades complete the scope.
Wates Construction is using a standardised, repeatable design for the houseblock, with pre-manufactured components assembled on site. That approach reduces programme time, improves quality control, and enables consistent environmental performance across multiple sites. The building is fully electric, designed with low-carbon operation as a core requirement.
The project targets BREEAM Excellent under the BREEAM New Construction scheme, reflecting the Ministry of Justice’s commitment to sustainable public sector infrastructure. Achieving that rating shapes every design decision on the project.
This is a live project currently on site, and the information published here reflects what Wates Construction have made publicly available. Build Energy’s involvement sits within the contractor’s technical supply chain.
Our Role
Build Energy provides two specialist services on this project. Both contribute to the BREEAM Excellent target and the building’s overall envelope quality.
Daylighting Modelling
We carried out a Hea 01 daylighting assessment for the new houseblock, covering the quantity and distribution of natural light across occupied spaces. On a prison houseblock, daylighting matters for two reasons: occupant wellbeing and BREEAM credit compliance. Our assessment uses simulation software to model the daylight factor (DF) across habitable rooms and communal areas, identifying where the design meets required thresholds. Where it does not, we advise on glazing sizing, orientation, and internal layout.
The Hea 01 credit requires a meaningful proportion of floor area to meet daylight factor targets. However, a four-storey houseblock presents challenges here: the floor plate is deep, and upper floors have less access to external daylight. We therefore begin modelling at RIBA Stage 3, so that glazing specifications and room geometries can be optimised before the design is fixed. Our reports are formatted for submission to the BREEAM assessor and include the evidence required to demonstrate credit compliance.
Air Tightness
We provide air tightness consultancy across the design and construction stages of the houseblock. At RIBA Stages 3 and 4 we carry out desktop drawing reviews, assessing the continuity of the air barrier around the building envelope. That focuses on junctions, penetrations, and openings, which are the most common sources of air leakage on new builds. We then issue written recommendations to the design team and subcontractors before work begins on site.
On completion we carry out the post-construction air pressure test, a fan pressurisation test that confirms the building’s achieved air permeability. A new-build scheme targeting BREEAM Excellent typically aims for 5 m³/h.m² at 50Pa or better. Design-stage consultancy significantly reduces the risk of a poor result, avoiding costly remedial works and re-tests late in the programme.
Our MOJ Framework Experience
HMP Wayland is one of several active Ministry of Justice projects where Build Energy provides technical consultancy. We work embedded within the supply chains of tier 1 contractors on the MOJ framework. Projects we can name include HMP Norwich and HMP New Hall, Wakefield , both Wates Smartspace Video Conferencing Centre schemes delivered under a separate programme. We have also provided BREEAM evidence for HMP Exeter’s new visitors building, delivered by Vinci Construction on behalf of HMPPS. Build Energy works on a large number of Ministry of Justice and wider government schemes across the UK but many are covered by confidentiality or security restrictions.
Working on live prison sites demands careful planning, because restricted access and security protocols affect every site visit. For air tightness testing, access to the completed envelope must be arranged well in advance. We plan these activities as standard and build them into our project programmes from the outset.
Find out more about our work across the justice estate on our justice and MOJ framework practice page.
Frequently Asked Questions
What does daylighting modelling involve on a new prison houseblock?
Daylighting modelling calculates the daylight factor (DF) across occupied rooms and communal areas using simulation software. The model is built from the architectural drawings and calculates how much natural light reaches interior spaces under an overcast sky, the standard condition used in BREEAM assessments. The results identify which rooms meet the minimum daylight factor thresholds for BREEAM Hea 01 credit compliance. Where rooms fall short, we advise on glazing sizing, floor depth, and internal surface reflectances. Modelling from RIBA Stage 3 lets the design team make changes before glazing specifications are fixed.
What is air tightness consultancy and how does it differ from just the test?
Air tightness consultancy covers the full process of achieving a good result, not just confirming one at the end. It begins at design stage with a review of architectural drawings, assessing the continuity of the air barrier at junctions, around openings, and at service penetrations. We then provide written advice and marked-up drawings to the contractor and subcontractors. That design-stage input significantly reduces the risk of a poor result at the post-construction pressure test, and with it the programme and cost implications of a failed test.
What BREEAM rating is HMP Wayland targeting?
HMP Wayland targets BREEAM Excellent or better under the BREEAM New Construction scheme. For daylighting, that means achieving the Hea 01 credit, with a meaningful proportion of occupied floor area meeting minimum daylight factor targets. For airtightness, BREEAM New Construction awards Ene 02 credits on a sliding scale, and achieving 5 m³/h.m² at 50Pa or better contributes credits. Targeting Excellent means both services must perform well, since there is limited scope to compensate with credits elsewhere.
What is the Accelerated Houseblocks Delivery Programme?
The Accelerated Houseblocks Delivery Programme is a Ministry of Justice initiative to rapidly increase prison capacity in England and Wales. Instead of designing each houseblock from scratch, it uses a repeatable design built from pre-manufactured components constructed offsite and assembled on site. That reduces programme time, improves consistency, and makes it easier to embed environmental performance standards across multiple projects. HMP Wayland is one of several sites where the approach applies, with Wates Construction among the contractors delivering it.
Does Build Energy work on live construction sites at operational prisons?
Yes. Build Energy works on active Ministry of Justice projects in live custodial environments, and on a large number of other MOJ and government schemes across the UK. Most cannot be named for confidentiality or security reasons. The projects we can name include HMP Norwich and HMP New Hall, Wakefield, both delivered by Wates Smartspace. Working on a live prison site requires advance security clearance, escorted access for all personnel, and compliance with the establishment’s operational protocols. For air tightness testing, test dates must be coordinated well in advance. We are familiar with these requirements and build them into our project programmes as standard.
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