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IAQ: Breathe Easier
two humans and in the o ce there is one. The furniture—beds, individual room sur-
Products, Research and Advice for Improving Indoor Air Quality wardrobes, kitchen counters, table chairs—are represented in their face area to the total Level Heating Requirement (W)
simplest form in order to reduce the simulation’s complexity while level surface area.
keeping a level that does not impact the results’ accuracy. The second Office 151.57
The air ow will be simulated in the three apartments and the o ce, approach consists of
through four distinct air volumes. The heat could be transferred from installing under oor Ground Floor 949.34
one air volume to the other by thermal conduction through the oors heating that will gen-
and ceiling. The slabs between the apartments are assumed to be erate an even tem-
plain blocks of concrete. perature distribution First Floor 1,197.87
The case scenario shows the residential building in winter in the rooms. Both of
conditions, with an outdoor temperature of negative and a these heating meth- Second Floor 1485.42
humidity rate of percent. ods will be imple-
mented and compared in this project.
Component U-value (W/K.m )) INDOOR AIR QUALITY
2
To maintain the indoor air quality in the dwellings, and prevent
Walls 0.2 the stagnation of harmful compounds such as carbon monoxide, a
constant renewal of the air must be ensured. In recent residential
Windows 1.6 buildings, such as the one presented in this case study, this air
renewal is performed by mechanical ventilation means in the
Door 0.2 form of extracting units placed at dierent locations around the
apartment, typically in toilets facilities, bathrooms, and kitchens.
Roof 0.13 The air introduced in the room would come from different
air intakes, located as far as possible from extracting units, to
Office Floor (above garage) 0.13 maximize the volume under the stream and taking into account
“zone air distribution effectiveness” as per ASHRAE .. It
The building is relatively new and has good insulation of its main recommends, for example, a supply of air from the ceiling for
components. The insulation quantity used for this project is the better eectiveness.
thermal transmittance (or U-value) and is described as per EN ISO One of the most-used ventilation rate measures is the outdoor air
as the rate of transfer of heat through a material. This can be rate calculation presented in the ASHRAE . standard for indoor
a single material or a composite. The table below summarizes the air quality.
U-values used in this project. Therefore, the indoor air quality can be ensured by maintaining
su cient air renewal. The minimum outdoor air rate, which is the
HEATING STRATEGY amount of air that needs to be introduced in the apartments, is
The main objective of this project is to guarantee the thermal comfort dened by ASHRAE . as:
of the dwelling’s occupants; this heating power selection is essential
in the design process. There are many heating strategies available to Vbz = Rp x Pz + Ra x Az
the architect and the HVAC engineer in order to reach an acceptable
and uniform temperature in the apartments. Az = Zone floor area (m )
2
The strategy adopted in this project is to implement radiators at
dierent locations throughout the rooms, typically under the win- Pz = Zone population
dows. The hot air that the radiators generate raises and acts as an WHERE Rp = Outdoor airflow rate required per person (l/s. person)
air shield against the cold air at the windows surfaces, and enters
through small gaps to reach the center part of the rooms where the Ra = Outdoor airflow rate required per unit area (l/s)
occupants are most likely to be present.
Using the U-values, surface areas, and heat transfer coe cients From ASHRAE . and for a residential dwelling unit, R is .
p
(external and internal) of the building’s components, one can L/s and R is .¢ L/s.m , for a m space occupied by two people.
a
approximate the heat power necessary to reach a temperature of This gives a Vbz of . l/s.
°C (.°F) taken as a reference for thermal comfort temperature. As a baseline, the outdoor air ow rate will be distributed equally
The summary of the calculations is shown in the table below for among the three extracting units for each at (£.l/s or .g/s of
each level. air)—one in the kitchen, one in the bathroom and one in the toilet
It can be observed that in this approximation, the heat being trans- room. The air at the intake, from the outdoor, is ltered. It has come
ferred from one apartment to the other through the thermal conduc- through a double- ow controlled mechanical ventilation (CMV) in
tion of the slabs has been neglected. The power generated by each order to heat up its temperature by heat exchange with the exhausted
individual radiator can then be determined by the pro-rata of each air. It is set to a temperature of °C.
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