The guiding thread throughout the entire design for the extension of the office was sustainably responsible construction. Both in the concept phase, with the taking of engineering decisions, and in the setting out of installation technical measures each time consideration was afforded to a rational and economically responsible solution.
Footprint and orientationConceptually this is translated into a compact, functional building with a limited footprint. The built-up surface area was thereby kept smaller than the existing building, although it was built a floor higher.
In this way, the footprint is reduced and the usable space is filled up more optimally.
By orienting the building to the North, this full facade was able to be interpreted as a glass facade. The northern lights served as ideal lighting in the office.
The construction of the ground and floor plans was made up of two parts. Leaning on the existing office, a long empty space ran through the building both horizontally and vertically. To the right of this empty space, the space is open plan.
The ground floor houses the reception area and the meeting facilities. On the first floor are the individual offices, while above the plan was set up as a landscape office.
Building techniqueThe choice of materials for the building was among others made as a function of the indoor climate. The load-bearing structure of the building is made up of concrete columns and floors with a high thermal mass. All interior walls on the other hand are light partition walls, meaning that the flexibility of the building remains guaranteed.
The very highly insulating shell is vertically made up of a load-bearing concrete wall separated from a hung panel in exposed concrete. The cavity wall was fully filled with PIR insulation.
For the roof, the choice made was PIR roof insulation, PVC roofing and a gravel ballast. This ballast increases the lifetime of the roofing, slows down downspout, avoids heating up the roofing and in addition provides a more attractive appearance.
HVAC conceptThe concept of sustainable construction goes a lot further than building in itself. In addition to the building of an airtight and highly thermally insulated building, energy management is also of crucial importance.
Central in the HVAC concept is air-conditioning with energy consumption that is as low as possible and directly connected to this CO2 emissions that are as low as possible.
In order to achieve this objective, an HVAC concept was thought up that is twofold:
- heating with relatively low water temperature and cooling with relatively high water temperature;
- ventilation coupled with natural cooling
Concrete Core Activation (CCA)In the new building, we chose concrete core activation (CCA), a sustainable air-conditioning method. Concrete core activation is a heating and cooling concept whereby water-carrying pipes are worked into the floor and ceiling construction. By optimally addressing the thermal mass of the construction parts, heat or cold can be stored, to be given off at a later point in time. At night the buffer and the concrete mass are loaded up and during the day the stored heat or cold is given off.
The giving off of the stored heat or cold begins as soon as the thermal balance between room temperature and surface temperature is disturbed. As the difference between the two becomes greater, the heat or cold release increases. In this way, falls and peaks in heating and cooling needs are smoothed out. This makes it possible to cool with relatively high temperatures and to heat with relatively low temperatures. In this way, for 24 hours it was possible to obtain an optimum temperature and comfort without the inconveniences of a traditional system.
By contrast to a floor heating system, the water-carrying pipes are not laid in the floor coating, but are embedded in the concrete construction. As a result, the total floor package is used for the storage of heat or cold.
In the winter situation, the building is heated by allowing water with a supply temperature of max. 29°C to circulate. The even spreading of heat given off ensures a uniform room temperature. In summer the opposite occurs. By sending cooled water into the piping network, at approx. 18°C, the spaces are cooled without the intrusive air flow of a traditional air-conditioning system.
Concrete core activation gives off the highest output via the upper surface of the floor since hot air rises. With cooling, however, the underside of the floor gives off the highest output. For these reasons, the suspended ceiling surface was reduced to a minimum so that a maximum surface area can serve for the cooling and heating of the spaces.
AcousticsInherent in the way in which the building is designed, a large amount of attention is dedicated to acoustic comfort. As a result of the large wall and ceiling surface in exposed concrete required for CCA, the fully glazed North facade and screed as a floor finish, there was a shortage of acoustically absorbent material.
The appropriate solution for the reaching of an accurate reverberation time (T60 value)¹ was found in the specific finish of the light partition walls and the suspended ceiling section and through the addition of acoustic sliding panels for the glazed parts to guarantee privacy.
¹ T = (0.161 x volume) / (sum of all wall surface x their absorption coefficient)
T60 = time required to reduce the noise level by 60dB
Heat pumpConcrete core activation - based on a very low temperature heating (VLTH) and high temperature cooling (HTC) - is the ideal heat output system for a heat pump.
We chose to use soil heat as a heat and cooling source for the heat pump. It is in particular the case that as of 5 to 7 metres depth a virtually constant ground temperature of 10 to 12°C is predominant. This heat is extracted from the soil using vertical soil heat exchangers.
The coolant that circulates in the heat exchangers takes up the heat from the deep soil layers. On extracting the heat from the soil, the ground temperature around the heat exchanger will drop during the heating season as it is higher than the supply from the surrounding undisturbed soil. As these same heat exchangers are also used to cool the building, the extracted heat is added to the soil. In this way, it is possible to ensure that the balance between heat extraction in the summer remains in equilibrium and the exhaustion of the soil is avoided.
The task of the heat pump is to further raise the temperature of the heated liquid in the heat exchangers through a process of vaporisation and condensing until the required flow temperature for concrete core activation is reached. The logical consequence of this is that the energy consumption compared to that of a traditional heating system is drastically reduced.
The new office was fitted with energy-efficient mechanical ventilation incorporating heat recovery.
With such ventilation arrangements, the air is mechanically supplied and sucked out in order to obtain optimum air quality. The fresh air is supplied via the suspended ceiling and blasted into the spaces sideways. The soiled used air is sucked out through the grills under the suspended ceiling.
Important in this was the insulating of all supply channels so that the supplied air retains the set start temperature, thereby ensuring that the cooling or heating effect is not reduced.
In addition, a heat exchanger with 90% efficiency is used to limit heat losses.
Soil tubeIn office construction, it may be assumed that for the overwhelming majority of the time, cooling has to take place. This for the simple reason that there are sufficient internal heat gains that provide for the heating of the building. The largest impacts in this regard are on the one hand the electrical appliances (computers, photocopiers, printers etc.) and on the other hand the people employed.
In addition to the cooling capacity provided by concrete core activation, secondary cooling was also provided. The freshly blown in outside air is sucked in via a soil tube. This air must follow a path in tubing that is laid beneath the building at a depth of around 1m. As in summer the soil at such a depth has a certain coolness, the air sucked in is pre-cooled before it is blown into the rooms.
In the winter, the principle works in reverse. The overly cold outside air is pre-heated through the underground path by the heat store in the soil. After this, the pre-heated air flows over the heat exchanger, which ensures that the heat from the air sucked out is transferred to the air blown in. This is done in order to be able to provide additional heating for the building.
In the between-season period, the outside air in itself already has an ideal temperature. As this air does not need to be cooled or heated, it is not sent through the soil tube and over the heat exchanger, but is sucked in via a by-pass and blown directly into the rooms. The sucking in of outside air via this by-pass functions on hot days above all also as night cooling to allow the fresh night air to circulate throughout the office.
LightingIn addition to an integrated study for the air-conditioning and ventilation concept, the lighting was also subjected to a simulation.
The fully glazed North facade ensures optimum light intake in the offices, meeting space and reception area.
The additional lighting is controlled on the one hand by a presence detector and on the other hand by a daylight sensor. The aim of this is to reduce energy consumption still further by only switching on the lighting when the room is being used and insufficient natural daylight is coming in.
In addition, the lighting was switched in parallel with this glazed facade. It is also thereby possible to automatically dim the lighting in zones using the daylight sensors to the extent that the light intake is weaker or stronger. A conscious choice of light colours was made for the walls and floors so that the incoming light is reflected in the spaces.
All these measures ensure optimum comfort is guaranteed with minimum energy consumption.
Solar panels (PV)In order to complete the loop for the design of a fully sustainable building, we chose to install photovoltaic solar panels on the flat roof. In this way, the sunlight electricity generated can either be used for own users in the building or can be 'sold' to the energy provider.