Tag Archives: Building Performance

Technical Risk Assessment for Low Energy Retrofits

Fuel poverty is one of the most important issues facing British households, today. In 2012, the number of households in fuel poverty in England was estimated at around 2.28 million, representing approximately 10.5% of all English households (DECC Fuel Poverty Report 2014).With rising fuel costs, it is critical that homes are refurbished to make them more energy efficient to relieve some of the stress on family budgets. The Greater London Authority has committed to supporting low-energy refurbishments on homes owned by local authorities and housing associated in the London boroughs.

The Greater London Authority (GLA) established the RE:NEW Support Team, funded by the European Investment Bank (EIB) and operated by Capita  to help local authorities and housing associations in London assist their residents by retrofitting homes. As part of this work, Six Cylinder Ltd led a specialist team, including Rickaby Thompson Associates and ArchiMetrics Ltd, to create a risk assessment process to evaluate the technical risks of different retrofit measures used for low-energy domestic retrofits. The process is uniquely aimed at evaluating and addressing the risks when various retrofit measures are combined and explaining the technical risks of retrofit in plain English.

The assessment toolkit includes a triage risk matrix to plot retrofit measures against each other with respect to the degree of their technical risk. Each retrofit measure has its own inherent risk rating and a rating when combined with any other measure. A risk score from 0, indicates measures have little or no impact on one another, whereas 3, indicates measures have inherent vulnerability and require careful design and execution. The matrix also shows which measures should be considered together, and which should never be used in combination.  At the design level, the matrix enables teams to assess which measures work well together and which combinations will have inherently higher risks and may require specialist support to ensure that this risk is mitigated.

For example, a housing association may be planning to upgrade an estate to make it more energy efficient and reduce the tenants risk of living in fuel poverty. The designer or assessor has advised a set of measures including external wall insulation, loft insulation and draught proofing and the installation of solar thermal. Each of these initiatives has inherent risks in isolation. However, in combination, the risks can be amplified. The insulation improvements will mean there is a higher risk of under-ventilation, which could lead to condensation problems and air quality issues. As such, it is vital to ensure that the retrofit account for ventilation which provides adequate air changes to the entire home to manage moisture and air quality. The matrix and risk assessment process allows the client team to progress the project, whilst transparently managing the technical risks with strategic expert advice, from the earliest possible stage of a retrofit. The assessment toolkit also includes Retrofit Watch Points, a list of high-level considerations for the Assessment, Design and Installation and Handover Stages of the project, as well as plain-English tips for key things that need to be considered with each retrofit measure.

For further information on the RE:NEW Support Programme please see GLA’s website  www.london.gov.uk/renew or contact Matt James at Matt.james@capita.co.uk

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The sole responsibility for the content of this webpage lies with the authors. It does not necessarily reflect the opinion of the European Union. Neither the European Investment Bank nor the European Commission are responsible for any use that may be made of the information contained therein.

Performance Anxiety

Good intentions are one thing, but how do we really know how well our buildings measure up?

human-crash-test-dummy-1

Science is what you know. Philosophy is what you don’t know. —Bertrand Russell (1872–1970) English philosopher, mathematician

By Lisa Ann Pasquale

The days of architects justifying design decisions with interpretations of esoteric philosophy are all but numbered. Wright rearranged clients’ furniture, Le Corbusier’s roofs leaked, and Mies van der Rohe’s Farnsworth house is the epitome of dysfunctional Modernism. Contemporary clients, however, are less accommodating (and more litigious) and rarely consider hubris a desirable quality in the person paid to design the roofs over their heads.

Architecture is a unique form of commercial production in that every building is a prototype — our crash-test dummies are, generally, the previous client. Each building has a unique combination of form, use, construction, systems, site, and project team, each with an impact on performance, energy, environment, cost, and quality. Assurances to clients ride on a plethora of assumptions. The only way to establish if the assumptions are valid is to revisit buildings after occupation, and systematically and objectively monitor, measure, and evaluate their performance. Similarly, the only way to substantively move the practice of architecture forward is to establish practice methodologies based on solid, scientific evidence rather than intuition and anecdote.

The idea is not new. First developed in the 1970s, post-occupancy evaluations (POEs) took a “real world” scientific approach to assessing the performance of buildings and, by extension, the built environment. Incorporating a host of comparative methods, these were typically conducted about two years after occupancy of new buildings and addressed how well the buildings met user needs, their environmental performance and, in some instances, their operating and projected lifecycle cost.

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Traditionally, POEs were associated with recently built projects, especially those with ambitious energy and environmental targets or unique technologies. Thus, they generally did not address the energy impact of the existing building stock and had little influence on retrofit and renovation efforts. But perhaps the greatest failing of the approach was its lag time: project teams received feedback years after the initial design work. Designers often felt that their thinking and methodologies had self-evolved enough in the intervening years that the feedback was no longer relevant, making it difficult to change design practices. To ensure that critical lessons took root, feedback needed to be integrated more effectively into the project process, and evaluators needed to assess and report on buildings that designers felt still represented the pinnacle of their technical prowess.

Building Performance Evaluation (BPE) has evolved out of decades of efforts to address these issues. BPE refers to a broader application of POE and scientific assessment techniques; unlike POE, it extends into the construction phase and can be easily applied to existing structures and renovations. In construction phases, these techniques are used as an advanced means of quality control. Triple air-pressure tests, for example, verify airtightness at key stages of completion to ensure that detailing and construction methods are meeting the intended technical standards. Periodic quality checks also ensure that construction crews develop their own skills and processes to more effectively monitor their own work. They also maintain a dialogue about quality between the design and construction teams so that specifications and details can be improved with input from builders. This is a clear advantage to teams who consistently work together.

Thermal anomalie around an electrical blanking plate
Thermal anomaly around an electrical blanking plate

The process has uncovered problems with “rules of thumb” and regulations, sometimes sending designers unexpectedly back to revisit the fundamental principles of good design. A recent co-heating and thermography survey of masonry townhouses built to 2006 regulation standards in the UK showed massive heat losses through the roofs above party walls. Previous regulations assumed that heat loss from dwellings through party walls was zero. However, the study consistently showed that poor detailing and construction resulted in thermal bridges, a lack of cavity closures, and air gaps, which drove convection currents in the cavities. These were acting as thermosyphons, drawing heat from the adjacent units into the cavities and then to the outdoors through the cavity roof and walls, accounting for up to 30 percent of the building’s total heat loss. Findings like these have the potential to change industry-wide practices, influencing both regulations and strategic investment.

BPE can also serve to test theoretical assumptions and calculations. For example, field tests that measure the heat flux and thermal conductivity through walls have shown variations ranging from roughly 5 percent to 20 percent of theoretical values, with certain constructions and fabrication techniques consistently more reliable than others. This empirical knowledge of inherent variations is applied in Scandinavia, where designers adjust the theoretical thermal conductivity values of construction assemblies twice in design calculations to give more realistic predictions of completed performance. They factor in one variable to account for uncertainties in the properties and dimensions of building materials and the resulting inconsistencies in craftsmanship, and another to adjust for the effect the assembly complexity has on its performance. This prevents them from assuming that an overly complex construction that is difficult to implement on site is more thermally effective than it’s likely to be.

Although construction-phase monitoring can improve quality, and scientific assessments can evaluate technical assumptions, they are still not enough to ensure that performance expectations are met. In 2009, the Usable Buildings Trust and Building Services Research and Information Association (BSRIA), both based in the UK, launched the “Soft Landings” framework to respond to the need for immediate feedback and increased user support as well as to provide the opportunity for more extensive assessments. Studies had found that buildings were not used as designers envisaged, often because of misunderstood design intentions, poorly executed design features, and inadequate user training, sometimes with drastic effects on energy use and performance. Soft Landings is intended to increase the intensity of designer engagement both before and after initial occupancy. A residency period during the first weeks of occupation gives the design team a structured time period in which to carry out quality assessments that must be done while the building is operational, Risk Registerto support and advise the client and users, and to learn from working in their own building. The process is akin to “sea trials” in naval architecture, where a boat’s design and robustness is tested in real-life scenarios as part of the commissioning process. In practical terms, Soft Landings aids in risk management by using BPE methods to anticipate problems.

But perhaps the greatest value of Soft Landings is its potential to boost the quality and rigor of the research that is key to ensuring relevant lessons are extracted and that the root causes of problems are addressed appropriately in future projects. The whys are always more important than the whats. For example, data collected on a new primary school as part of a two-year joint BPE research project between Architype Ltd. and Oxford Brookes University showed a spike in gas use over the summer break. The detailed nature of the data-collection methods allowed researchers to identify exactly the weeks in which the boilers were burning, which led them to the cause: When the boilers were serviced just before the summer break, the mechanicHandoverAftercare overrode the automatic controls to check his work but never re-engaged them when he left, leaving the boilers running all summer. The findings led to specific recommendations to the client for improved management and modifications to the designer’s own client-handoff process (a more formal, extended process in the UK than it is in the US), to reduce the likelihood of similar problems on future projects.

The temptation is to sanitize findings such as this and to give a figure for the buildings’ potential performance without operational slip-ups — a temptation that should be resisted. The X-factor effect of the occupants’ presence is as important as the quality of the building’s design and construction. Designers must accept that their buildings are rarely used as they anticipate, however frustrating that may be. The haze of unrealistic expectations will dissipate with comprehensive knowledge of how buildings are used and also lead to more robust assumptions in design phases, better expectation management, more realistic predictions of performance, and reasonable expectations of occupants. The all-too-human tendency to overpromise and underdeliver is not one that the profession will survive in a competitive environment. But firms that see opportunity in these techniques can develop more comprehensive services for clients who understand the difference between assuring and ensuring performance.

Although BPE is a science, it’s not an exact science. Sometimes spurious data is recorded (such as when schoolchildren make a game of breathing on a CO2 sensor to make the count on the digital readout go up and down), and sometimes the answers from scientific analysis are ambiguous, with no clear resolution. Not all problems have simple solutions; scientific answers can be more baffling than the questions. However, every question has a means of investigation, and although the complexity of buildings in operation can be overwhelming, ignorance should not be the accepted default. The scientific evaluation of building performance is the only way for our industry to move forward and meet the expectations of the societies we serve.

Originally published by ArchitectureBoston 

Thermal Imaging Podcast

Had a really great chat with Ben, from @HousePlanningHelp, talking about how to use thermal imaging to detect and correct construction defects. These can impact the energy and environmental performance of buildings, and can contribute to the Performance Gap between design intentions and in-use energy performance.

Tune into (or download!) the podcast to learn more about how thermal imaging can help quality-assure the performance and integrity of the building fabric.

Thermal anomalie around an electrical blanking plate
Thermal anomalie around an electrical blanking plate

Text from House Planning Help 052: Identifying Construction Defects by Using Thermal Imaging Cameras

Lisa Ann Pasquale from Six Cylinder Limited explains what thermal imaging is and how it can be used in quality assuring the construction of low energy buildings.

Interview with Lisa Ann Pasquale

Lisa Ann Pasquale is an architect by training but after several years supervising construction works in Boston, USA, she took a masters in building physics from the Architectural Association.

With practical experience under her belt she frequently found herself shooting holes in her professor’s theories about perfect construction! It was at this point he suggested that she might be suited to becoming a post occupancy building performance evaluator and that’s exactly what she did.

Thermal Imaging Allows Us to See Differences in Temperature

While part of the electromagnetic spectrum is visible to the human eye (visible radiation – light) there is a lot more that we do not see.

Thermal imaging allows us to look at infrared radiation, which is a slightly different wavelength, and deals with the heat of objects.

If you point a thermal imaging camera at your hob when you’ve just cooked a meal, you’ll see it glowing red. Likewise if you open your fridge it’ll be black or blue. So it allows us to see differences in thermal temperatures.

When it Comes to Buildings, Thermal Imaging Helps Identify Anomalies

Thermal anomalies are significant differences in temperature which wouldn’t normally be expected.

For example, you would expect a wall to have a fairly consistent temperature from top to bottom and thus it would be the same colour on the thermal image.

This image below shows air infiltration where some sealing tape was accidentally missed around a door and window. This caused large amounts of cold air (the black patches) to flow into the room, through the interior wooden wall cladding. This was noticed using thermal imaging in the later stages of construction and corrected by the builder before the building was handed over to the client.

Cold-Air-Infiltration

Rainscreens Can Mask the Defects

In certain situations it may be difficult to get meaningful thermal images.

Rainscreens, which are often cladding that is a certain distance away from the rest of the building fabric, make it very difficult to see if there’s a problem (from the outside). However, the defect would still show up on the interior pictures.

This is one of the reasons why thermal imaging should be carried out on interior surfaces as well as exterior surfaces.

Depending on the Project, Thermal Imaging is Useful at Different Times

Ahead of a retrofit it makes a lot of sense to carry out a thermal imaging survey. This is because you want to be certain you know what is going on and that you’re not about to insulate damp building fabric.

In a new build, thermal imaging is unlikely to take place until the heating system is commissioned.

Most Defects During Construction are Accidental

Lisa says it’s relatively rare that a building defect is down to blatant negligence on the part of a contractor. More often than not a tradesperson has forgotten to do something and just needs to go back and fix it.

An example of this might be an electrician who scoops out some insulation to install a socket and then just slaps a plate over it without putting some insulation back. Therefore a cold spot would show up on the thermal image.

Poor Design Can Lead to More Significant Issues

Detailing is very important to get right. If it’s not done correctly, heat can be conducted directly from inside to outside. This also increases the risk of condensation (where warm, moist air will come into contact with a colder surface).

Beware of the ‘Drive-by’ Survey!

When it comes to organising a thermal imaging survey Lisa says: “It’s not a particularly well-established practice. It’s not super common to do it. It’s becoming more common which is really positive.”

Even people who are certified to do this as a service may not be a good choice. This is because they are not invested in the process and are just there to take a few snaps. You want someone who takes the time to understand what’s going on and looks for specific details that might be an issue.

The Right Conditions are Necessary to Achieve a Meaningful Survey

The weather conditions need to be right to conduct a thermal imaging survey. They are mostly done in winter and on overcast days. If the sun is out it will heat up the external walls and if it’s rainy or windy there will also be issues.

Doing it at night or early in the morning can be an option, too, because this is about the infrared spectrum and not the visible light spectrum.

At Least a 10-Degree Temperature Differential is Necessary

The temperature inside needs to be at least 10 degrees hotter than outside and this is achieved by artificially boosting the temperatures by running the heating system for a few hours.

Before the photos are taken the radiators are allowed to cool (so they don’t show up in the pictures!).

The Images Must be Calibrated Properly

It’s important to make sure that the camera is calibrated for the emissivity of the material that’s being measured.

While bricks, woods and concretes are all in a similar range other materials, such as zinc, are not. Therefore you’ll get a false reading unless the camera is re-calibrated.

Thermal Imaging Provides a Quality Assurance Process

Lisa tells a story of how she spotted a serious building defect when just messing about with a thermal imaging camera on-site at a children’s centre.

After hearing about it the contractor quickly realised that a sloppy tradesperson had slapped up some trim and cladding without putting in any sealing tape around the windows and doors, etc.

The issue was quickly fixed. If it hadn’t been remedied the client would probably have ended up with mould, condensation and rot on the inside of building.

 Interpreting Images Requires Expertise

Thermal imaging is a great tool but it’s important not to overestimate what it can do. These photos will be no good without a person who can interpret what is going on from the image and suggest the best course of action.

The example below shows the outside of a building on a cold morning (pre-dawn). The bright red/yellow colour indicates that heat is escaping the building via a detail around a large beam. This is creating a thermal bridge at the top of a glazed curtain wall, allowing heat to move from the inside of the building to outside.”

Exterior-heat-loss

Ask Your Architect a Few Questions about Thermal Imaging

If you are building a low energy house then thermal imaging should form part of the quality assurance process. So when you are hiring an architect, it is worth seeing if they are familiar with it. Lisa says: “If this is something that is completely foreign to an architect I would be a little bit hesitant about working with them to design a low energy building.”

Report

A sample report

Certain Information Should be Included in a Report

  • The day and time that photos were taken
  • The emissivity of the target surface
  • The approximate distance that the camera was looking. Ideally all images should be taken at right-angles to what’s being photographed (so that the whole image is at the same distance from the lens), but that is not always possible with building details.
  • The building plan or relevant detail is often helpful to have alongside the images so that you can orient the images or see which detail caused an issue.
  • The reports should have a covering page noting the time/day of the survey, the site weather conditions (wet, snow, overcast sky, sunny,wind speeds, etc) and the conditions for the previous 4-6 hours and matching visual and thermal images, amongst other details.