Interview with Anders Tennerhed

Published 2023-10-05

ECiS – Energy Concept in Sweden AB is a company that offers solutions to save energy, reduce environmental impact and improve the indoor environment both in buildings and/or processes. Anders Tennerhed from ECiS works with indoor climate analyses and also collaborates with Nordtec as a course leader for our indoor climate courses. We met Anders and asked him a few questions about indoor climate analysis and ECiS.

Who are your clients and why do they need your help?

– For our part, we can say that there are two directions. On the housing side, there is often a need to investigate cold apartments. It must not be due to the building envelope, but perhaps because the heating systems are incorrectly adjusted or the ventilation flows are incorrect.

– But it could also be that some apartments have a poorer climate screen due to large leaks in or around windows, or that an office space has been converted into an apartment and that it has not been properly adapted to its real purpose.

– Then we have a lot of public clients, and then we talk about premises, such as hospitals or that we work with office premises where the staff feel that the climate is not good.

Which parameters affect the perceived indoor climate?

– These include air temperature, temperature from surrounding surfaces, humidity, which is measured with an IAQ sensor, and also air velocity, i.e. air movement in the occupied zone, which is measured with a draught sensor.

– The temperature of surrounding surfaces can be measured with a special type of sensor called a globe thermometer.

– You may also need to consider the thermal insulation capacity of clothing (clo-tal), metabolism (physical activity) and heat exchange between bodies.

How does an indoor climate analysis work?

– During an indoor climate analysis during the heating season with a testo 400 it is attempted when the outdoor temperature has been at zero or colder for at least three days. This will have an impact on all the different structures of the building.

– Measurements are taken and logged for 3 minutes at each measurement point, resulting in 180 measurement values from which the instrument can calculate PMV and PPD values, which gives a measure of how good the indoor climate is at each measurement point. It is also important that the instrument has had time to acclimatize for about 20-30 minutes before the measurement. So this is not something to be rushed.

– In parallel with the testo 400 measurement, all structures are also examined with a thermal imaging camera to see if there are any constructional deficiencies such as leaks or cold surfaces. Smoke is also released at expected cold spots such as cold exterior walls, windows and air leaks in facades to see how much “cold draft” there is or how leaky the building envelope is. Smoke is also used in larger zones where there is a risk of draught problems and at the same time all air flows and air movements in parts of the building where there are complaints are measured with different types of instruments.

– They also measure the supply and exhaust air temperatures from the ventilation system to see how well it works. During the measurement period, it is also important to note external conditions such as outdoor temperature, wind direction, wind speeds, air pressure and whether it is overcast or sunny. There are many parameters that need to be taken into account when making measurements.

This IR image taken with a testo 872 shows that the plinth under the rebuilt window section only holds about 12-13 degrees at +3 degrees outside.

What is the interest in indoor climate?

– The interest of our clients actually seems to be increasing, I think. We have quite a few repeat customers and they understand the value of doing a proper investigation of recurring problems with the indoor climate. Usually, many problems can be eliminated by building technology, or it is a question of adjusting the heating or ventilation system.

At which points do the measurements take place?

– There is something called the occupancy zone , outside of which the criteria set do not apply. According to BBR (Boverket’s building regulations), the occupied zone is 0.1 meters above the floor up to 2 meters above the floor as well as 0.6 meters from walls and 1.0 meters from external limitations such as windows and doors.

– You never measure outside the occupied zone, because there you can never maintain the same climate that the building is designed for.

What are the requirements/standards for the right indoor climate?

– There are actually several claimants. For example, BBR, Boverket’s Building Regulations, current OVK regulations and AFS 2009:2 – Workplace design. In the case of complaints from tenants in apartments, you can also rely on the Public Health Agency’s guidelines.

What are the most common complaints that lead to an investigation?

– An indoor climate investigation usually starts with complaints from users, i.e. staff in offices or tenants in homes.

– Taking apartments as an example, the most common complaint is that it is too cold in some part of the apartment.

– If it is a workplace, it is common to find it draughty or cold. These faults are often caused by excessive airflow from the ventilation system or a leaky climate screen. During the summer, we may also be contacted to investigate when it gets too hot indoors due to a lack of shade.

What are the most common errors?

– Common faults can be neglected maintenance on windows, doors, damp facades, etc. or misadjusted heating systems or air flows. It could also be an incorrect construction of walls, windows, etc. for the workplace in question. Sometimes it can also be the case that a workplace has been set up in premises that are not at all fit for purpose, which poses major problems that need to be resolved.

– But the most common thing in premises is that you have incorrect airflows that are not adapted to the needs of the current activity, which often creates draft problems. If the caretaker takes the “easy” route, the supply air temperature of the supply air is increased, which makes things worse with a decrease in ventilation efficiency. People are easily chilled by excessive air movement. Based on this, it is therefore important that all airflows are adapted to the current activity when changes are made to all buildings.

Do you have an example of an investigation and what action was taken?

– A good example is when premises were converted into apartments in a governor’s house in Gothenburg about 10 years ago.

– A governor’s house is built of brick on the first floor, often on a granite base, with two floors of wood on top. So the technical conditions of the building envelope are completely different between the different plans.

– When the premises on the ground floor, which had previously been a tobacco shop and pizzeria, were to become apartments, problems arose after the move. The rebuild replaced all the large windows with a new insulated structure, but missed the plinth sections and the cold floors which had no insulation down to a cold cellar.

– The perceived indoor climate with these cold surfaces is not good, even if an indoor temperature of about 20 degrees is maintained. The operational temperature (perceived temperature) in these converted apartments was very low. Unfortunately, the tenants had to be evacuated after moving in and these eight apartments had to be rebuilt to achieve an acceptable indoor climate.

– A positive effect of this investigation, which led to further rebuilding, was that energy use was greatly reduced in the apartments and the tenants were satisfied with the indoor climate.

---