Case Studies - Air Tightness Consultancy & Testing

If this school were sitting a zero-carbon design exam it would get a very good mark. This star pupil is Montgomery Primary School in Exeter. Its Passivhaus design cuts energy use to an absolute minimum. Working with Bam - the Main Contractor, HRS Services were responsible for the Air Tightness Testing throughout the project.

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The implementation of Building Legislation Part L2 has caused many retailers to look again at the design of new buildings. In order to set a benchmark for future developments. IKEA employed the UK's largest fan to check the air tightness of its Glasgow store.

HRS's Megafan features a two-metre fan that can impel air up to a rate of 90cu metres per second - three times greater than any other test rig in the UK. It is mounted on a lorry and allows more efficient tests to be carried out than by using a number of smaller units. The Megafan confirmed that the building passed Part L2 requirements and helped suggest where further improvements could be made.

HRS have been involved with design issues on a number of archives, the most important being the new archive for the British Lending Library in Boston Spa. The BLL archive has to reach an air leakage target of <0.5 m³/hour/m² - which is comfortably the tightest specification to be reached by any building in the UK to date.

HRS have been involved throughout the contract process from advice at the initial design/specification phase through to reviewing contractors tenders proposals, contractors design proposals, on site audits, on site testing of components through to final air testing of the building.

Powys County Council appointed HRS Services to carry out comprehensive air tightness, smoke and thermographic testing on a school to ascertain the extent and cause of drafting problems. The drafting problems were so severe that in winter the school had to be moved to a warmer building as it was imposible to heat!!

Problem

Powys County Council needed to understand the full picture of why the school was drafty and cold. They knew from their own investigations that air leakage was a problem. However, their objective was to identify where and how air leakage occurred and whether other factors played a part, in terms of design issues, poor standards of construction and lack of insulation and how they might be remedied.

Air Tightness, Smoke Test and Thermographic Survey Carried Out

On a cold, overcast day in February, HRS Services turned up on-site with the full range of air tightness testing equipment. An air tightness test and smoke test was carried out on the whole building. Subsequently, a thermographic survey of the external envelope and a detailed visual inspection were carried out. The complete report was made available to Powys County Council on CD with a summary of where the problems were located and their extent.

Remedial Solution

HRS identified that the biggest air leakage path was through linear open joints in glulam beams which acted as purlins through out the school. The total area of beam joint which was open from all rooms in the school to a cold open roof space was 2 m2. The open joint could be easily accessed along it's full length form inside the school and be closed off by installing a backing rod and sealant.

Building Envelope Performance Issues – A Complete Solution For Investigating, Analysing Problems and Providing Solutions

Building envelope performance issuesare usually brought to light by occupants complaining of draughts or being too cold or hot usually in winter or the height of summer. The one common issue for facility managers / building services managers and occupants are that these problems are long standing, difficult to diagnose and even harder to remedy.

The most important aspect of solving each particular problem is having the tools and skills to investigate the problem fully to arrive at a proper diagnosis of the causes.

HRS have at their disposal a combination of analytical techniques – (design reviews, energy audits, U value calculations, thermal modelling etc) with on site investigative techniques – (thermal imaging surveys, air tightness tests, smoke tests, visual surveys, on site data collection) to make a diagnosis of the building performance issues being exhibited. Allayed to this are the wide ranging skills and practical experience of HRS staff that has been built up over the last 15 years which allows the problem to be correctly diagnosed.

To date a large number of problems have been successfully dealt with on 100’s of buildings ranging from retail stores to hospitals, offices, data storage centres and factories.

The correct diagnosis of the problems then allows remedial solutions to be  specified, designed and put forward which address the fundamental causes and not the symptoms of the problem. Once specifications have been fully discussed and assessed with the client; they can be costed and carried out by HRS Services, thus providing clients with a totally packaged solution.

Each of the case studies detailed below have had the initial problems solved, to the relief of everyone.

Improving Air Tightness Results and Overall Building Performance

In 1995 HRS Services were approached separately by SAFEWAY and TESCO to tackle cold draughts and heating problems on a number of retail stores; which in periods of inclement winter led to stores being closed. The store closures were obviously very costly in terms of lost business but raised other personnel and Health and Safety issues. Overall the serious building performance problems spilled into other areas of the business and the over riding  requirement was to solve the cause of the draughts  and heating problems.

HRS carried out surveys to the stores and identified that their were significant holes in the building envelope which led to higher than specified air change rates, which heating systems could not overcome. HRS was able to specify and cost remedial works to air seal the external envelope of the stores.  At that time stores were objectively measured on their building performance by air  testing the whole store for their overall air tightness, which was specified to be < 5 m³.hour-1.m-². For comparison purposes, the current Building Regulations commercial buildings have to attain a maximum air permeability of < 10 m³.hour-1.m-².

After works were complete the performance of the stores improved markedly which led to HRS been awarded roll out programmes to tackle a number of other stores.  Notable successes were made including raising the ambient temperature within 1 store by 5°C in winter!!

To date, HRS have fully utilised the experience and skills gained by successfully improving the building performance of over 500 retail store nationwide.

Pic above: Thermal image of external elevation of store highlighting hot air leaking from cladding

Decants Pupils Due To Heating Problems

Over a number of winters the envelope performance of a low energy ‘green’ school, built with sustainability in mind, with well insulated walls, roofs, triple glazed windows, green oak timber etc failed significantly exhibiting low internal temperatures and draughty classrooms. The problems were so severe that pupils had to be decanted to other schools on a regular basis.  HRS were brought in and used a number of on site investigative techniques – air tightness test, smoke test, visual survey and thermal imaging camera – to investigate potential defects.

The  main defects found were open joints between GLULAM beams and plasterboard throughout the school and poorly fitted doors. The defects were highlighted effectively using thermal imaging cameras and the results confirmed using a smoke leakage test – refer to photos below and a visual  survey.  The affects of these defects on the air change rate per hour was corroborated with a full building air tightness test which confirmed that the total leakage area was excessive leading to a high air change rate.

These remedial works to defects were specified and subsequently sealed during the school holidays. Since that date the performance of the school has improved markedly and no pupils have had to be decanted.

Pic: Digital and Thermal Image Indicating Air Leakage Around Glulam Beams

Problems With Heating In Winter and Cooling In Summer

A 4 storey, 10 year old, large office building was difficult to heat in winter and cool in summer, particularly on the ground floor which led to personnel issues from complaints, working conditions etc. over a significant length of time.

After discussions with the client it was agreed to initially carry out a full thermal imaging survey and visual survey to the building.

The  major  defect found were a large number of missing profile fillers on various elevations, which allowed significant air leakage from the atrium at high level.

Remedial works were costed for the client after undertaking a full building survey.

Pic: Thermal images identifying significant air leakage through open profiles

Patients Decanted Due To Severe Cold Draught Problems

Soon after opening, patients had to be decanted from a HD Unit due to severe cold draughts and low temperatures on wards. The estates team thought that insulation had been omitted from walls and requested a thermal imaging survey be carried out.

After discussions with the client it was agreed to initially carry out a full thermal imaging survey and internal investigation of the building. The  major  defect founds were;

• a large number of missing profile fillers on various elevations which allowed cold air ingress

• leakage from behind various flashings and cladding junctions

The main contractor for the hospital carried out extensive remedial works to rectify the problems found.

Pics - top: Elevation and Thermal Image Indicating Air Leakage From Cladding
Pics - bottom: Internal Digital Image and Thermal Image Identified Missing Profile Fillers and Cold Air Ingress

Ingress Of Flies To Medical Research Labs - Building Energy Performance Case Study

Over a number of spring and autumn seasons the ingress of flies into South and East facing offices and laboratories caused significant problems for building occupiers. The flies were not only a health risk but were very annoying for researchers to find them day buzzing around their heads, day after day!! . Not inducive to clear rational thinking, apart form how to swat them.  Despite close surveillance and numerous attempts to identify how flies gained access, no route of entry or solution could be found by the estate management team.

The estate management team called HRS after being recommended of our air sealing services on retail stores to best practice levels and thought there might be some complimentary skills which could be useful to them. Initially, HRS visited the building and after discussions with occupiers and facilities managers and carrying out close visual inspections both internally and externally across all elevations of the hospital; it became apparent that inadequate cladding at parapet level allowed fly ingress into the roof void above suspended ceilings and behind dry lining. This was simple to identify due to daylight being observed!! Once in, the flies found open cracks and gaps behind dry lining and escaped via cracks and gaps into the building and into offices via light units in suspended ceilings - where they could annoy everyone – very effectively.

Over a 1 week period HRS gained access into rooms and effectively fly sealed cladding and dry lining with fire rated materials, thus leaving researchers able to research in peace!!

Problems With Heating In Winter and Cooling In Summer

A 3 storey, 10 year old, large commercial office building was difficult to heat in winter, particularly on the top floor; which led to cold air draughts coming down through the suspended ceiling and persistent complaints from personnel about a poor  working environment. After discussions with the client it was agreed to initially carry out a full thermal imaging survey and visual investigation around the eaves and verges. The  major  defects found were;

• Large areas of missing thermal insulation around eaves/verges

• Large gaps around parapet details.

• Open cavities into wall void at eaves/verges

Remedial works were specified to install a 70 mm rigid insulation board around eaves and verges, which was to be sealed to the roof  and wall cladding. HRS successfully carried out the remedial works and to date the problems have been successfully alleviated.

Pics above: Digital Location Image and Thermal Image At Eaves – Internally
Pics below: Elevation Image and Thermal Image At Eaves Showing Heat Loss