Laboratories are a very specific form of non-residential building. Moreover, the term describes a very heterogeneous mixture of usages, ranging from light-duty, slightly extended office use to heavily ventilated buildings with very strong internal heat sources and hazardous substances in the extract air.

That said, there cannot be a general solution to „the“ Passive House laboratory. Optimised solutions are possible for specific combinations of ventilation demands, internal heat gains, occupancy and usage. The wider the range of possible usages to be accommodated, the more investment in potentially underused plant will be required and the more refinement for all kinds of part-load conditions will be necessary.

Nevertheless, some general guidelines can be given. Many will sound familiar and straightforward to anyone who has designed Passive Houses before. PHPP is a reliable companion to tell what to expect:

The usage of a laboratory building is subject to changes and may alternate between different scenarios over the lifetime of the building fabric. While the latter lasts 50+ years, the lab equipment, building services, and particularly, the MVHR equipment will be replaced before that. Consequently it is reasonable to design the building fabric for a scenario with low internal heat gains, for example comparable to an office building. For cool-temperate climates, this will automatically ensure sufficiently high internal surface temperatures for thermal comfort and safety against any moisture-related damage. Radiators beneath the windows are dispensable.

Given the high share of investment in building services systems for a laboratory building, the marginal extra spending on improved fabric quality is not very significant. Given the long-term flexibility it provides for the usage of the building it might be considered a no-regret measure.

Well-accessible thermal mass can be beneficial, particularly when internal heat gains fluctuate considerably. Acoustics measures to control the reverberation period should leave the concrete slab exposed, which suggests suspended baffles. For daylighting reasons these should be oriented perpendicular to the façade.

Laboratories and offices share some other aspects, such as the importance of lighting. The design should balance good daylighting with limiting solar loads in the summer, which will result in moderate openings around 40% of the facade, with external movable shading that still allows daylight in. In many cases this will mean some sort of venetian blinds with daylight-transporting horizontal slats in the top part. Ideally the window openings will have no lintel to allow light to the depth of the room, but a parapet, where glazing will not contribute to daylighting. As glazing is usually the most expensive part of the building fabric this will also optimise building cost. An internal glare screen can help ensure visual comfort for screen work in the winter, when exterior shading is not desired.

Daylight will be complemented with highly efficient, LED lighting with illuminance and presence control. A qualified lighting design will ensure an optimised solution with installed power of less than 1.5 W/(m²*100lx) that limits the high illuminance to the actual workspace.

For laboratories with high ventilation requirements the ventilation heat loss is clearly the dominant heat loss mechanism, which makes MVHR choices decisive as regards the total energy use. As a precondition for efficient MVHR operation very good airtightness will be required (≤ 0.6 m³/(m²h) @ 50 Pa). As laboratory buildings tend to be large structures this poses no substantial challenge though, employing the usual techniques and materials available for Passive House buildings.

Just as other Passive House buildings laboratories operate on supply-air only, of course there is no recirculation.

The heat recovery options depend much on the usage. Office use will allow any heat recovery method, but as some form of lab-specific ventilation requirements will always be present, a regenerative heat recovery is normally ruled out. However, in cases with not very hazardous experiments an MVHR with plate heat recovery is an option. It may demand improved internal air sealing and/or fan placement to direct internal leakage in the safe direction but has been successfully applied (cf. Examples). Heat recovery should strive to achieve an effective heat recovery rate of 85% which results in very bulky units. Roof-top installed systems require no internal space and thus save cost.

All air but insignificant exceptions (e.g. from an acid storage cabinet) must pass the heat recovery.

If acutely hazardous substances must be handled, they may be treated in a separate MVHR system based on a run-around loop. This has the downside of greatly reduced heat recovery rate, rarely better than 70% and rather less. An exhaust air heat pump may assist, but the overall efficiency will be lower than the passive plate heat exchanger.

If the bill calls for handling hazardous extract air all-around the only reasonable option is a run-around loop with exhaust air heat pump as the primary system. Such systems will benefit from being supplied by a single source as a preconfigured, preassembled and coherently controlled package, very much like the Passive House compact units for houses.

As high airflow rates cause high heat losses as well as demanding high fan power, the airflow should be actively managed to just meet demand. This will involve shutting down ventilation during off-hours or at least switching to a strict minimal-flow idle state. It may benefit from presence control. Any fume cabinets will modulate their extract air flow depending on the slider position and regular room extract air flow will be reduced accordingly. As in any Passive House building, the ventilation system(s) will operate in balance with regard to the building envelope at all times. In some cases a separate, small MVHR system for night work places may be a consideration.

Keep in mind, that all heat recovery systems will have a lower limit for the flow they can handle with good heat recovery rate. Beyond that the flow regime will change to laminar and the heat recovery may plummet. Therefore, if the scale of possible flow scenarios is very wide, a combination of smaller MVHR units may have to be cascaded. The same holds for exhaust air heat pump systems and their compressors.

Flow controllers should network with the MVHR unit for fan control in order to avoid the inferior constant duct pressure regime for increased efficiency.

All ducts require a large cross-section in order to limit air speed/pressure loss and save fan power. Any filters and fittings need to be laid out for low pressure loss as well. Ways should be sought to design a compact, short-path duct system without narrow bends- a point where the systems design and the architectural design should be developed in sync.

High air flows offer a high potential to meet comparatively high loads by ventilation air alone. A good fabric will keep the heating load low enough to be manageable with air flows typical for office-like use, but higher loads, particularly in the summer, can be handled by the plant that will usually be designed for higher intensity ventilation.

For example, at 8 ACH (as is typical for many lab scenarios) 50 W/m² can be handled by ventilation air alone with a temperature difference of only 6K. This is very heat-pump friendly and facilitates an all-electric building based on renewable energy- which in turn results in a favourable PER rating.

If an exhaust-air heat pump is all it takes for heating and cooling of the space this has a potential for a simple, compact and affordable plant with minimal maintenance. It may take a learning curve for the market though, to supply such systems in a preconfigured, almost off the shelf way as is now (2022) common for boilers and their auxiliaries.

While all load handling should be possible by ventilation air alone in most instances, it can be a consideration to also employ concrete core activation of the slabs. Then a considerable part of heating and sensible cooling can be handled independent of MVHR operation- a useful option if the MVHR is shut down over night or to boost total capacity in a heat-pump friendly way. However, in climates with high humidity levels other cooling strategies must be chosen.

In humid areas where dehumidification is required but no ERV is possible due to hazardous extract air, a very efficient dehumidification system for large air flow must be devised. This will- and can without hygienic issues- employ the most efficient heat recovery to reheat the dehumidified air with the heat from the incoming, moist air. The condenser of the dehumidifier heat pump in the exhaust air path can be operated in wet mode, after filtering and UV disinfection of the condensed water.

Some biological laboratories may require thermal disinfection of waste water. In a conventional system the water’s high thermal capacity will cause a very high energy demand, and commercial systems already feature some form of heat recovery. However, for disinfection only a high level of temperature is required, not heat. If the heat recovery is sophisticated enough to achieve a high heat recovery rate and heats up the incoming water with the heat of the water that is simultaneously displaced from the tank and if the system is well insulated, then only a minimal heat loss needs to be covered. A high-temperature heat pump can do the job and transfer heat from the run-off back to the tank.

As commercial units may not be satisfactory, trigger the work on a bespoke system early on. Indoor swimming pool technology has come a long way in heat recovery from waste water in recent years and may offer interesting solutions.

In cases where exhaust air filtering were stipulated, it may be worthwhile to consider extract air filtering in the root branch and benefit from more options for MVHR under this premise.

In a cool-temperate climate a typical lab with a ventilation rate of 8 ACH daytime and night time off, combined with 85% heat recovery on all ventilation air can limit the space heating demand to ≤ 30 kWh/(m²a). The basic cooling demand can be very low as well, but is largely driven by the internal heat gains from the actual lab equipment. Ways should be sought to procure the most efficient equipment available, but frequent changes and limited availability of alternatives to highly specialised apparatus defines a limit.

Therefore, Primary Energy (Renewable) demand may be high compared to office buildings and be treated according to the directions given in the Certification Criteria on an individual basis.

New lease models may become conceivable given the lower and more dependable energy use, e.g. with budgets for energy included in the monthly payment thus giving an incentive to the users to actively contribute to efficient operation.

Built and pilot-certified by PHI in 2012 for the State of Saxony Agricultural Research Institute in Nossen/Germany. Three structures with 5000m² lab space and 1600m² administration and canteen.

MVHR with counterflow plate heat recovery was possible due to the nature of the targeted research. Waste water thermal disinfection for part of the lab (EPPO rules). Load handling over both ventilation air and concrete core activation. Supplied by a combined heat and power system within the building. Due to the low flow temperatures this could easily be replaced with a heat pump.

Download the project brochure with good illustrations (descriptions in German language).

Mixed use, office, lab and support on 2500m². Pilot-certified by WARM

Multi-use lab and prep spaces pilot-certified by WARM

Biological field research lab on Lake Michigan pilot-certified by PHI.