Residential Ventilation – Needs, Trends and Expectations

Claus Händel

Technical Secretary

EVIA European Ventilation Industry Association

Brussels

claus.haendel@evia.eu

The increasing airtightness of our homes places new demands on residential ventilation: on the one hand ensuring occupants a good indoor climate, on the other hand protecting the building from damage caused by excessive air humidity. Legislation requiring ever lower energy consumption, combined with the expectations of adequate ventilation, presents a challenge for the ventilation market.

Keywords: Indoor Air Quality, Ventilation System, EPBD, EVIA

Buildings account for approximately 40% of overall energy consumption in the EU and for 36% of greenhouse gas emissions. Alongside non-residential and industrial buildings, residential buildings constitute a major source of emissions and energy consumption.

The Energy Performance in Buildings Directive (EPBD) aims to encourage EU Member States to facilitate the market transition to Nearly Zero Energy Buildings (NZEBs) with a very high energy performance. Whilst the drive to secure energy efficiency improvements is a laudable objective, the demands for energy savings is seeing our homes become increasingly airtight.

In turn, this places new demands on residential ventilation: on the one hand ensuring occupants a good indoor climate, on the other hand protecting the building from damage caused by excessive air humidity, e.g. mould growth.

Legislation requiring ever lower energy consumption, combined with an expectation of adequate ventilation, presents a challenge for the ventilation market. It is therefore important to choose the right solution, rather than focusing on the cheapest options.

Indoor Environment Quality and Indoor Air Quality.

Currently the main political and economic targets of the EPBD are energy savings, environmental impact and the cost of that. We forget that buildings are not built to save energy, money or emit low levels of CO2. Buildings are fundamentally designed to protect humans by providing shelter from the cold, heat, rain, sun, dust, wind etc. Furthermore, buildings should not only provide protection from the elements, but should also ensure a high level of Indoor Environment Quality (IEQ) including:

·         Indoor Air Quality (IAQ),

·         thermal comfort

·         lighting and acoustic environment

Modern European citizens spend on average over 90% of their time indoors. Indoor air originates from outdoors, carrying outdoor air contaminants indoors with varying degrees of penetration: some are effectively transferred indoors (e.g. for PM2.5 penetration ranges from 50–90%), others are adsorbed on indoor surfaces or readily react with indoor air co-pollutants (e.g. ozone). In addition, indoor environments themselves contain sources of contaminants, which, due to the rate of air exchange in comparison to outdoor environments, can contribute considerably to high pollutant levels. Indoor environments have been widely studied for a range of chemicals and biological contaminants; in the presence of indoor sources, indoor concentrations of contaminants are higher, sometimes 10 or 20 times higher (e.g. formaldehyde), than those recorded in outdoor environments.

Figure 1. French National IAQ Survey, CSTB.

In combination, the generally higher indoor concentrations of contaminants and the overwhelming fraction of time spent by individuals indoors, mean that indoor air pollution is the dominant source of air pollution exposure regardless of whether the sources are indoors or outdoors. Indoor Air Quality is a complex result of occupant’s activities, human responses, source emission, and contaminant removal.

Most indoor air pollutants arise from chemicals, through the use of cleaning products, air freshener and pesticides, and via emissions from furniture and construction materials, as well as from heating and cooking. Cooking emissions, for instance, have long been seen primarily as an odour problem. However, recent field studies showed that Particulate Matter (PM) is a significant health risk of indoor air (Logue, 2013) and cooking can be a major source of PM2.5 [2].

In addition, outdoor sources can contribute considerably to indoor air pollution. Microbiological contaminants which may induce allergies and asthma also require consideration as indoor air pollutants. Examples of potential serious effects include respiratory disorders, including asthma and cancer.

Figure 2. Health Effects of indoor air quality. [1]

Whilst CO2 is considered as non-toxic, very high levels (typically not in residential buildings) have been shown to cause health problems for occupants.

However, from an indoor air quality standpoint, CO2 is a surrogate measure for indoor pollutants emitted by humans as it is correlated with human metabolic activity and humans are the main indoor source of CO2. Unusually, high indoor levels of CO2 can cause occupants to grow drowsy, develop headaches and suffer from impaired activity levels [3] (Figure 3). Indoor CO2 levels are an indicator of the adequacy of outdoor air ventilation relative to indoor occupant density and metabolic activity; with the highest levels of CO2 typically recorded in bedrooms. Therefore, interior CO2 levels are used as a scientifically accepted method of measuring how efficient a ventilation system is at maintaining the ventilation rate required to refresh the air.

Figure 3. Impact of CO2 on Human Decision-Making Performance. Error bars indicate one standard deviation. [3].

Humans are the main indoor source of CO2. Indoor levels are an indicator of the adequacy of outdoor air ventilation relative to indoor occupant density and metabolic activity. Typically, the highest CO2 levels are measured in bedrooms. Thus, interior CO2 levels are a useful way to measure how efficient the ventilation system is at maintaining the ventilation rate required to refresh the airflow.

Considering the aspects stated above, we can summarise the requirements for a residential building and its ventilation. The Building is

·         energy efficient and uses renewable energy,

·         gives protection from any inside and outside harmful impact,

·         provides a good and healthy indoor environment,

·         and operates automatically and in a user friendly (smart) manner.

Residential Ventilation Systems

Europe has a wide range of climate zones and a big variety of building and construction traditions. This leads in parallel to a wide range of ventilation solutions for different applications. This is an advantage, because the building owner may select his preferred solution.

We distinguish the following different ventilation systems and strategies:

•         Single technology systems

o   All natural

o   All mechanical (either centralized or local)

§  extraction only (MEU)

§  positive input ventilation

§  bidirectional ventilation with heat recovery (HRU)

•         Multiple or hybrid technology systems

These systems may be equipped with:

·         Demand control (CO2, humidity, VOC, presence)

·         Heat recovery (Air/Air or Air/Water with a heat pump)

·         Smart feedback options

·         Filtration (depending on the system options)

The energy impact of ventilation systems is covered in European and national EPB calculation rules, as lead down in the EPB standards. The energy rating of the ventilation products is declared according the Ecodesign and Energy Labelling Directives.

However, there is a distinct lack of information on IAQ performance. To correct for this discrepancy, EVIA is supporting the development of an IAQ calculation procedure [5] with the ambition of providing better information on the performance of residential ventilation systems and units in relation to IAQ.

Residential Ventilation Market.

Modern residential ventilation systems provide high levels of IAQ at a low energy consumption. Therefore, it is surprising that up to now approximately 60% of the building stock in the EU has no dedicated ventilation system (Figure 4) [5]. The consequences are growing issues with mould and poor IAQ. For ensuring good IAQ it is essential that provisions are made to encourage proper installation of ventilation systems in the renovation market.

Figure 4. Ventilations systems in Building stock. [5]

In most Member States, there are requirements to install dedicated ventilation systems in new residential buildings. There is however no EU legislation dealing with the issue of IAQ in renovation and there is no provision in the EPBD requiring IAQ information to be included in the Energy Performance Certificates. The architect, designing engineer, consumer and users of the building are required to take decisions with insufficient guidance on IAQ impacts, with the associated risk that designers might pursue and consumers seek energy optimisation at the expense of efficient ventilation.

Despite this drawback, the ventilation market has grown robustly in recent years due to the introduction of the EPBD. Mechanical extraction units (MEU) still dominate the market, but heat recovery units has begun to constitute a larger share of the market.

Figure 5. Ventilation in Europe. [6]

However, the picture does vary significantly from Member State to Member State, in large part due climate variations. Nordic Member States tend to have a larger share of Heat Recovery units, in a moderate climate there is more or less a balance and in Southern Member States MEUs and intermittent fans remain the norm.

Variation among Member States is illustrated effectively by comparing the French and German markets. In Germany, a strong rate of growth is evident in sales of single room units with heat recovery and units with an alternating air flow (push-pull) which are directly mounted in the façade.

In France, heat recovery units represent very small market share of about 5%, in contrast to some markets where the market share for MEU/MVHR can range from 60/40 to 50/50 in new-builds.

Is this enough? As EVIA we say no, because problems with bad IAQ are growing much faster, and regulations (national and European) has to take notice of this fact and should provide:

·         Minimum requirements (either national or European)

·         Consumer information in existing documentation and EPC.

Smartness of a Ventilation System

Could “smart home” solutions provide the answer to our issues?

If we listen to the ongoing discussions, some people might think so, forgetting that nobody knows what “smart” really means in this context. A definition cannot extend only to a simple connection to any network which allows for remote on and off, or changing the operation hours or setpoints.

Smartness could mean that IAQ sensors (CO2/VOC/Humidity/temperature) are used to continuously measure and monitor ambient conditions in the house and provide real time feedback to a zone controller which manipulates the ventilation rate to match the specific use and occupancy of the building whilst ensuring the lowest possible energy consumption possible.

A recent European study [8] on smartness and user behaviour concluded that “Home Energy Management systems as a combination of intelligent controls for heating ventilation and lighting consistently result in the lowest primary energy use for the lowest cost …
The fact that innovative intelligent control systems can currently not be valorised within the official Energy Performance evaluation tools of the different EU member states clearly slows down the large scale deployment of these promising energy saving measures.”

In addition, smart ventilation systems could secure further energy efficiency improvements by informing the building owner when servicing is needed or what exact element needs replacing.

Therefore, any definition of smartness in the context of ventilation should include objectives beyond energy efficiency including:

·         Providing good IAQ using adequate demand control solutions,

·         high thermal comfort,

·         filtration depending on outdoor air quality,

·         service and maintenance,

·         network connectivity and functions.

Installation

New buildings, as well as renovations of the existing building stock, should aim not just for good energy performance but also for high quality standards with regard to the work undertaken, as this is a prerequisite for high building energy performance. Various experiences show that there are cases where the quality of the works is a (major) issue of concern [9]. Some EU Member States have imposed or will impose in the near future independent compliance checks to ensure the correct installation of ventilation systems.

Heat Recovery and Waste Heat

The Renewable Energy Directive (RED) recognises heat pumps as a renewable energy technology and it is commonly accepted that outdoor air is a source of Renewable Energy. In this context, other technologies using exhaust air (which will become outdoor air once it has left a building) should be treated in the same manner as renewable energy in the revised Directive.

There is no technological or physical reason to handle recovered exhaust air differently from ambient air (see Figure 7).

In highly efficient NZEBs, the heating and cooling power demand for ventilation is the dominant component of the energy consumption. The most effective device to “generate” or recover the heating and cooling energy demand is heat recovery in ventilation units (using passive systems or heat pumps in ventilation systems).

Figure 7. Energy flow in a building and renewable and waste energy.

Summary

The ongoing revision of the EPBD is a great opportunity to drive much needed improvements in the existing building stock and to promote systems and solutions that combine to deliver high Indoor Air Quality, low energy consumption and consumer empowerment. It is an essential tool to meet the EU’s climate and energy targets and improve citizens’ health, comfort and productivity. Therefore, EVIA and other organisations (REHVA among them) have requested the MEPs and the Member States to take up the following issues during the inter-institutional negotiations on the revision of the EPBD-directive:

1.    Ensuring adequate indoor air quality in European buildings

2.    Regular inspections of ventilation systems to achieve healthy and energy efficient buildings

3.    Compliance checks to ensure a correct installation

Literature

[1]                      Olliviera Fernandes et al. Health Effects of indoor air quality… REHVA Journal 4/2009 pp 13-17.

[2]                      Efficiency of recirculation hoods, Piet Jacobs, Wouter Borsboom, AIVC 2017.

[3]                      Is CO2 an Indoor Pollutant? Higher Levels of CO2 May Diminish Decision Making Performance; William J. Fisk, Usha Satish, Mark J. Mendell, Toshifumi Hotchi, Douglas Sullivan, Lawrence Berkeley National Laboratory Berkeley, CA; State University of New York Upstate Medical University Syracuse, NY.

[4]                      Methodology for assessing the air-exchange performance of residential ventilation systems Rob C.A. van Holsteijn, Jelle Laverge, William L.K. Li; AIVC 2017.

[5]                      Ecodesign Lot 10 Study and Supplementary Study, FGK, 2010.

[6]                      EVIA estimations on current ventilation market.

[7]                      FGK BDH statistics – residential ventilation units with heat recovery 2016

[8]                      Impact of user behaviour and intelligent controls on the energy performance of residential buildings, 3E, 2014.

[9]                      ICHAQAI - Impact de la phase CHAntier sur la Qualité de l’Air Intérieur, Charline Dematteo, 2017.