The result
Eighteen plots on a live residential site achieved Part F compliance first time across three ventilation strategies.
ATSPACE delivered ventilation flow rate testing using a readiness‑led approach, identified the few recurring issues that cause most failures, and worked with the contractor and M&E team to close them out before test slots were wasted.
The project avoided retests, avoided handover delays, and produced clear, reliable evidence for the compliance pack.
Project snapshot
Service: Ventilation flow rate testing
Client: Main contractor (mixed tenure housing)
Site: Willowgate Park, Phase 3, 1–18 Bracken Row, Warwick CV34 6TU
Building type: Houses + low‑rise apartments
Plots tested: 18
Ventilation strategies: System 1, System 3 MEV, MVHR
Programme stage: Pre‑completion + handover sequencing
Compliance driver: Approved Document F + linked Part L evidence expectations
ATSPACE delivery: Readiness checks, flow measurements, on‑site adjustments, fast reporting
Engineers: ATSPACE accredited ventilation test engineer + compliance coordinator
Why Part F flow rate testing becomes a problem on multi‑system sites
On mixed‑strategy sites (System 1, System 3, MVHR), inconsistency — not equipment — causes most failures.
Typical reasons sites lose time:
- plots booked before fans are commissioned
- MVHR left on default settings or filters fitted late
- System 3 MEV units not configured for trickle/boost
- terminals swapped or installed with wrong inserts
- crushed, long or badly routed ducting
- blocked door undercuts or missing transfer paths
- trickle vents closed or missing
- snagging changes altering settings after testing
The client wanted predictable compliance, not a test‑and‑hope approach.
What ventilation flow rate testing proves
Ventilation flow testing answers two critical questions:
- Is the ventilation system moving the air it should from kitchens, bathrooms and wet rooms?
- Can the dwelling replace that extracted air through background ventilation and transfer paths?
By system:
- System 1: intermittent extract performance + correct air paths
- System 3 MEV: continuous extract rates + correct configuration
- MVHR: balanced supply/extract + correct room rates
ATSPACE focuses on outcomes that stand up in the compliance file, not rushed readings.
What ATSPACE was asked to do
The contractor needed one testing partner for all ventilation types, with no impact on finishing trades.
The brief:
- deliver Part F flow rate testing across 18 plots
- reduce retests through readiness checks
- identify patterns early so fixes were applied once
- keep reporting fast for handover documentation
- work in a site‑friendly, low‑disruption way
What ATSPACE did on site
Step 1: Plot readiness checks before testing
We prevented wasted test slots by confirming each plot was truly ready:
- fans powered and commissioned
- correct mode available
- terminals fitted, not swapped or blocked by decorating
- MVHR filters installed + clean
- background vents fitted and open
- doors/transfer paths not blocked by flooring
- no ongoing work that would change results
- wet‑room layouts checked for air transfer
Step 2: Test sequencing aligned to access and plot type
We grouped similar plot types to keep:
- test conditions consistent
- access smooth
- site coordination predictable
This reduced delays and improved accuracy.
Step 3: Ventilation flow rate measurement + adjustments
For each plot we measured flow at terminals and adjusted where required.
System 1 (intermittent extract):
- confirmed fan performance
- checked installation consistency
- ensured transfer paths were unobstructed
System 3 MEV (continuous extract):
- confirmed trickle/boost configuration
- measured each extract valve and balanced accordingly
- checked duct routing + resistance indicators
MVHR:
- balanced supply and extract
- verified room‑by‑room rates
- confirmed boost function
- checked for swapped valves or incorrect inserts
Step 4: Fast reporting for compliance packs
ATSPACE delivered clear plot‑by‑plot results so handover documentation could progress without delay.
Key problems found and how we prevented retests
Problem 1: Door undercuts reduced by flooring changes
Reduced undercuts blocked air transfer.
Fix: Flagged early and corrected before testing to avoid borderline results.
Problem 2: MVHR supply/extract imbalance
Caused by default settings and valve inconsistencies.
Fix: Rebalanced dwelling totals, corrected room rates, locked in settings.
Problem 3: System 3 MEV valves inconsistent by plot
Valves were fitted correctly but not set consistently.
Fix: Standardised settings by plot type and gave the M&E team a reference.
Problem 4: Background vents closed
Several plots were set up incorrectly.
Fix: Added vent position to readiness checks.
Outcome
All 18 plots achieved Part F compliance first time, across all three ventilation strategies.
Project outcomes
- no retest cycle
- reduced disruption to finishing trades
- smooth handover documentation
- predictable, repeatable process for future phases
- fewer post‑handover ventilation complaints
Common mistakes this project avoided
- testing before commissioning was complete
- leaving MVHR on default settings
- ignoring door undercuts/transfer paths
- swapped or incorrectly set valves
- testing with closed vents or blocked terminals
- losing settings due to post‑test snagging
CTA
If you need Part F flow rate testing across multiple plot types and ventilation systems, ATSPACE will plan the programme, confirm readiness, test correctly and prevent costly retests.
Ask for
- System 1, System 3 and MVHR flow rate testing
- readiness checks to avoid wasted test slots
- commissioning support + balancing
- fast, compliant reporting for handover + Building Control
Frequently asked questions
Do you test System 1, System 3 and MVHR on the same site?
Yes — mixed‑strategy sites are common, and consistency is critical.
Why do plots fail flow rate tests most often?
Incorrect commissioning settings, duct restrictions, swapped terminals, blocked transfer paths, closed vents.
Can systems be adjusted during the test visit?
Yes — where agreed with the contractor, we make practical adjustments to achieve compliance and avoid retests.
