The Result
A new office scheme achieved Part L compliance sign‑off first time because the SBEM model remained aligned with as built services, not outdated early‑design assumptions.
ATSPACE produced the SBEM calculations, tracked design and procurement changes throughout delivery, and issued final BRUKL outputs in time for practical completion with a clean, defensible evidence trail.
Project Snapshot
Service: SBEM calculations
Client: Developer + design & build contractor
Site: Meridian Exchange, 44 Station Boulevard, Reading RG1 1LZ
Building type: 6‑storey new build office with reception + amenity areas
Floor area: Approx. 7,400 m²
Services strategy: All‑electric HVAC, mechanical ventilation, zone controls, metering
Programme stage: Practical completion window
Compliance driver: Building Regulations Part L (non‑domestic)
ATSPACE delivery: Design‑stage SBEM, iterative model updates, as‑built SBEM, final BRUKL outputs
Team: ATSPACE building performance engineer + compliance coordinator
Why SBEM Is Where Projects Lose Time
Part L issues on commercial buildings usually appear when the SBEM model falls out of sync with real‑world decisions.
Typical triggers:
- lighting layouts change but schedules aren’t updated
- zoning/controls altered during value engineering
- ventilation rates shift during coordination
- metering and BMS intent not recorded clearly
- specifications drifting across drawings, schedules and O&Ms
- commissioning decisions not checked against compliance impact
The developer wanted a calm route to completion — no last‑minute SBEM redesign, no Building Control queries, no scramble.
What SBEM Calculations Do in Practice
SBEM (Simplified Building Energy Model) is used to demonstrate non‑domestic Part L compliance.
The model is only as accurate as the inputs.
A compliant SBEM process requires:
- accurate geometry & zoning
- correct fabric & glazing values
- correct lighting & controls
- correct HVAC type, efficiencies & control strategy
- ventilation rates aligned with coordinated design
- correct metering & BMS description
- a defensible evidence pack for Building Control
ATSPACE treats SBEM as a managed deliverable, not a final‑stage document.
What ATSPACE Was Asked To Do
The contractor needed ATSPACE to:
- produce SBEM outputs and BRUKL reports
- keep the model aligned to design development + procurement
- minimise Building Control queries via controlled evidence
- deliver final outputs in time for PC
- avoid late‑stage redesign triggered by compliance drift
What ATSPACE Did
Step 1: Lock down a clear baseline model early
We created a baseline SBEM model with recorded assumptions and agreed:
- which elements were fixed
- which were likely to change
This prevented disputes later about what the model assumed.
Step 2: Short, targeted evidence checklist
Instead of asking for everything, we requested only the items that move compliance:
- lighting schedule + control strategy
- HVAC plant + efficiencies
- zoning + operating schedules
- ventilation rates + supply/extract strategy
- metering arrangement + sub‑metering
- heat‑recovery details where relevant
- any glazing/fabric changes
This cut down unnecessary email chasing and ensured no critical data went missing.
Step 3: Track model updates alongside procurement
As products and strategies were finalised, the model was updated immediately.
This prevented the classic “final‑stage shock” where the as‑installed strategy no longer matches the last compliant model.
Step 4: Focus on the high‑impact compliance drivers
For offices, the main compliance movers are:
- lighting + lighting controls
- HVAC efficiencies + controls
- ventilation rates + heat recovery
- glazing values & solar control
- zoning and schedules
We ensured none of these were left vague.
Step 5: As‑built confirmation before issuing outputs
Near completion, we conducted an as‑built review with the contractor + building services lead so final SBEM inputs reflected actual installation, not assumptions.
Problems Faced — and How They Were Solved
Problem 1: Lighting substitution late in programme
Lighting was changed due to supplier issues.
Why it mattered: lighting efficacy + controls strongly influence SBEM.
Fix: confirmed installed product metrics, updated model, avoided compliance drift.
Problem 2: Controls narrative unclear
Controls were installed, but documentation was weak.
Why it mattered: unclear controls = conservative SBEM assumptions.
Fix: worked with services team to document zoning + control strategy clearly.
Problem 3: Ventilation rates altered during coordination
Ventilation values changed when ceilings and plant zones were reworked.
Why it mattered: ventilation energy is a major SBEM factor.
Fix: captured final coordinated strategy and updated the model accordingly.
Outcome
The office scheme achieved Part L compliance sign‑off first time, with all final SBEM/BRUKL outputs delivered before practical completion.
Project outcomes:
- no programme delays due to SBEM
- reduced Building Control queries
- model aligned to as‑built services
- clean audit trail supporting handover documentation
Common Mistakes This Project Avoided
- leaving SBEM at design stage while procurement changes everything
- treating lighting substitutions as minor
- vague control strategies forcing conservative assumptions
- issuing final outputs without as‑built review
- discovering compliance drift only at the end
CTA
If you need SBEM calculations that support Part L sign‑off without last‑minute surprises, ATSPACE will keep the model aligned to the as‑built building and deliver accurate outputs in time for practical completion.
Ask for:
- SBEM calculations + BRUKL outputs
- model updates through design development
- as‑built SBEM review + evidence‑pack control
- fast, accurate completion‑stage turnaround
Frequently Asked Questions
What usually causes SBEM compliance issues late in the programme?
Design drift — lighting, controls, ventilation and plant selections change but the model isn’t updated.
Can SBEM stay aligned through design and build?
Yes — with a controlled update process and clear evidence checklist.
Why is controls strategy important for SBEM?
Controls heavily affect predicted energy use; if unclear, SBEM defaults become too conservative.
