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Managing energy for comfort

Heating, ventilating and cooling buildings to make them comfortable for users is a major consumer of energy. We have all sorts of sophisticated and expensive kit to do this but all too often building users are not comfortable. The first line of response is often to dial up more heating or cooling. The result is always bigger energy bills but frequently occupants are no better off than they were before!

This article explains the following key factors that influence comfort, other than the air temperature itself.

  • Keeping building users happy and saving 4_16-img-300-200-opt - Peter Hawtin - peterhenergy
  • What affects comfort?
  • Humidity: turning the heat up can make you feel colder!
  • Air velocity – over-ventilation wastes energy.
  • Radiant heating – the unwelcome power of the sun
  • Activity levels affect heating and ventilation requirements
  • Dressing appropriately
  • Cut complaints, improve productivity and save money!

Taking these into account in your HVAC strategy will lead to more comfortable, more productive, building users and cut your energy consumption.

You might also like to read the related article: Is your BMS Wasting Energy?

Keeping building users happy and saving energy

A major use of energy in buildings is space heating and cooling to provide thermal comfort for occupants. Any attempt to minimise energy consumption without compromising the comfort of building users has to be based on a good understanding of the variables that influence comfort and on how to design and implement a strategy to deliver it.

Heating, cooling and ventilation systems and associated controls are intended to deliver a constant appropriate internal environment for building users but all too often they are designed and managed with very little understanding of the thermal behaviour of the building and what actually makes occupants comfortable..

What affects comfort?

Apart from the actual air temperature there are five key variables which affect a person’s perception of temperature. These are: humidity, air velocity, radiant heat, activity level, and clothing.

It is imperative that these additional factors are taken into account when designing a strategy to maximise the comfort of building users and at the same time minimise the energy required to do so. Some of these factors can be controlled by plant; others require the education and participation of informed and engaged building users.

Humidity: turning the heat up can make you feel colder!

We feel most comfortable in an environment with around 65% air humidity. Heating air to raise the temperature reduces humidity and the dryer air removes moisture from the skin which has a cooling effect. Maintaining the correct level of humidity is essential to avoid wasting energy by overheating air to compensate for the cooling effect of low humidity.

Air velocity – over ventilation wastes energy

Air velocity also plays a major role in our perception of temperature. Air movement across the skin has a significant cooling effect and people working in draughty or highly ventilated areas will often raise concerns about feeling cold regardless of the actual air temperature.

The easy response to comfort concerns caused by over ventilation is to turn up the heating yet this is counterproductive and wastes energy. It does nothing to reduce any draughts and will reduce humidity and, where heating is provided by an air handling unit, increase ventilation – both creating a perception of cooling for building users. In our experience, massively over ventilated buildings are very common and can cause the greatest loss of heat from a building – in one case, increasing wall insulation made it worse!

Radiant heating – the unwelcome power of the sun

When designing a control strategy, radiant heating gains need to be taken into account. Using technology to harness solar energy for heating is now big business but passive solar heating has always been with us and the move in newer buildings to bigger windows has only increased this. Sunlight entering a building directly warms surfaces which radiate heat back into the room. Occupants will be warmed by both the direct solar radiation and by heat radiated from surrounding objects.

It is important to identify if a particular part of a building needs additional cooling or reduced heating due to radiant heating. In some cases it may be necessary to install solar shading or window film to reduce the solar gains as excessive radiant heating can create uncomfortably warm internal environments. Another solution for floor to ceiling widows is to replace the bottom half with insulated wall panels.

Activity levels affect heating and ventilation requirements

The more active we are the more heat we generate and visa versa. If building users are mostly sedentary this will need to be reflected in the level of heating. In areas where building users are more active less heating or more ventilation may be necessary. Ideally energy managers should have an understanding of the level of activity undertaken by occupants in the various areas of the building. Planning control strategies accordingly can greatly increase the comfort of occupants and reduce energy waste – for example by the opening of windows or use of air conditioning.

Dressing appropriately

In living memory a first response to feeling cold would be to wear warmer clothes, these days the first response is often to turn up the thermostat. Ideally occupants should wear clothing which is appropriate to their level of activity. Often, this is not the case and underdressed building users will query the space temperature of the buildings. Although it may be deemed inappropriate to suggest occupants wear more (or less) clothing, they should be educated with regard to the extent to which your organisation is prepared to heat and cool a building. The emphasis should be on how personal choices affect an individual’s perception of those standard conditions and enable informed decisions regarding dress to be made.

Cut complaints, improve productivity and save money!

As that heading suggests, a pro-active approach to managing energy for comfort has a triple bottom line for your business. It takes some time and thought, and it does mean engaging building users, but the benefits will be significant and often achieved for little or no capital outlay.

Your Independent RISK FREE Solutions

The above considerations are just part of the process of managing a Building Management System effectively. To ensure that your BMS is minimising energy consumption we suggest a Green Consultancy BMS Health Check or a BMS Audit. A Health Check investigates the “head end” only whereas the Audit includes the plant being controlled. Health Checks cost only £1,950 +VAT and typically identify tens or hundreds of thousands of pounds worth of annual cost savings.

All of our energy/carbon reduction services are based on our unique rigorous and scientific methodology – for full details please see Energy efficiency methodology

Put us to the test NOW! To discuss your requirements please call John Treble on 01761 419081 or email John@GreenConsultancy.com

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BMS Audit for University of Lincoln

“The University of Lincoln was very pleased with the report that The Green Consultancy put together for us. The report has enabled us to re-focus how our Building Management System is used to manage energy consumption and control the environment in academic spaces.”

Daniel Clayton, Environmental Sustainability Manager

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BMS Audits for West Mercia Constabulary

“We commissioned The Green Consultancy to undertake an ongoing series of energy investigations, including BMS Audits, at our head office and various police stations.  The service given and the treatment received has been excellent; a worthwhile investment to improve our energy performance. We are extremely satisfied with the results and are implanting the recommendations – and would recommend the Green Consultancy to our partner organisations.”

Kim James, Force M&E Officer

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University BMS Audit

The Green Consultancy carried out a BMS Audit of a university campus which identified over 70 opportunities to reduce energy consumption leading to a total reduction of over 2,000 tonnes of CO2.  Recommended BMS upgrades, adjustments and associated plant upgrades will reduce costs by £260,000 per year, and although there will be some implementation costs for plant upgrades, much of this can be achieved at low cost simply through improved management of the BMS. Maintenance issues accounted for £93,000 per year of the total annual savings identified.

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BMS Services for University of Worcester

Following a BMS Health Check we provided a new strategy and full tendering support for a replacement BMS.  These were some of the services delivered within a three year contract for energy management involving a consultant being on site for up to three days per week.

"The Green Consultancy have proved to be adept at understanding the requirements of a complex organisation across an extensive estate and have worked with colleagues in the University of Worcester to help us better understand our priorities in relation to carbon reduction.  Their support for the estates team is working extremely well and in addition to resolving issues and making efficiency gains, members of the in house team are also increasing their knowledge base. I would not hesitate to recommend them to others."

Mark Hughes, Director of Estates & Facilities

John Treble

Put us to the test NOW!

For over twenty five years we have been delivering superior outcomes for thousands of commercial, industrial and public-sector clients.

You need not take our word for it – hundreds of their comments are at the foot of these pages.

To discuss your requirements please call John Treble on 01761 419081 or email


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