One of the main reasons for global warming isthe sustained increase of CO2emissions, trapping heat and warming up the atmosphere. With more frequent storms, landslides or floodings, climate change willmake buildings more vulnerableand reduce their lifespan.As energy plays a key role in the management of buildings, in this article, we will discuss theconsequences of climate changeand increased CO2 emissions on thebuilding’s energy consumption and occupant comfort.For the following calculations, we will useBuilding Energy Modelling (BEM)to evaluate how an office building will behave in thenear(2050) anddistant future(2100) compared to theyear it was designed(2000).
As you might know,Dexmauses BEM for many purposes such assimulating the impact of energy efficiency retrofits,estimating the disaggregation of energy consumptions, or evaluating the impact of different scenarios.
Measuring the impact of Climate Change on Buildings: External factors
To represent the effect of climate change on buildings, we will focus on the following significant weather parameters for the built environment:
- Atmospheric CO2concentration in PPM
- Outdoor Air Temperature in ºC
- Outdoor Air Relative Humidity in %
The effect of other meteorological parameters like wind speed, solar radiation or rainfall has been neglectedwhether due to the lack of literature or due to the estimated low effect on the building behaviour.
勒t’s now look at these three parameters, their definition and their impact on the building’s performance.
1. Atmospheric CO2 concentration
Theatmospheric CO2concentrationis expressed in Parts Per Million (PPM) and fluctuated between 200 and 300 ppm in the past centuries.
Based onthe OECD Environmental Outlook Baseline projections,current atmospheric CO2concentration has been around400 ppmsince the 2000s, reaching a new threshold. Atmospheric CO2concentration is predictedto continue rising upto reach 530 ppm by 2050, and 780 ppm by 2100.
If we want to see these alarming numbers decrease, we are left with no choice but tosignificantly reduce our emissions. However, even if we were to stabilise our CO2emissions, unfortunately, this would not be immediately noticeable. Indeed,it takes time for the CO2emitted to be eliminated from the atmosphere naturally: whereas some cycles are fast and can eliminate CO2in 5 years, the absorption of CO2by the soil, the oceans or the vegetationcan take thousands of years…
2.Outdoor Air Temperature
The Outdoor Air Temperature, or Dry Bulb Temperature, is basically the one we refer towhen speaking about air temperature. It is called “Dry Bulb” because the air temperature is indicated by a thermometer not affected by the air moisture.
Based onthe same OECD projections,outdoor air temperature will increase, compared to 2000,by 土 2ºC by 2050 and by 土 4ºC by 2100.
This temperature change affects us all. It is causing regional and seasonal temperature extremes while reducing snow cover and sea ice, increasing heavy precipitation and changing the range of plant and animal habitats – expanding some and reducing others.
“The Earth’s temperature has risen by 0.08° Celsius (0.14° Fahrenheit) per decade since 1880, but the rate of warming since 1981 is more than twice that: 0.18° C (0.32° F) per decade”, as highlighted bythis Climate.gov report.
3.Outdoor Air Relative Humidity
Relative humidity (RH) is a measure ofhow much water vapour is in a water-air mixture compared to the maximum amount possible. It is given as a percentage from 0% (absolutely dry air, zero moisture content) to 100% (air saturated with moisture, any additional moisture will condense). There are fewer studies concerning the relationship between outdoor air humidity and climate change, butthe one from PNAS表明decrease in relative humidity of 0.2% per decade in the last 50 years(illustrated by graph C).
Combined with the increasing Outdoor Air Temperature (Graph A), the total amount of moisture (specific humidity) isin fact increasingas shown by Graph B.Study showsthatthis deadly combination of increasing heat and humidity could have many direct consequenceson health, productivity and could even lead to death even for healthy individuals.
The resulting weather conditions can be summarised in the following psychrometric chart (seeherefor more information about psychrometric charts),showing the higher dry-bulb temperatures and humidity ratios.
What does it mean for your Buildings?
Well…that’s a good question!
勒t’s now imaginean office building in Lyon in France, atemperate regionof Europe, built in the 2000s. We will assume a3-storey buildingwith aheat pumpfor the heating, and achiller for the cooling, with a building envelope corresponding to the standards of the year 2000.Thanks to Dexma’s BEM tool you will be able toestimate the impact of climate change on the building thanks to different indicators(IAQ, thermal comfort, indoor air temperature and humidity, HVAC energy consumption), and for 3 different climate scenarios we mentioned: the years 2000, 2050 and 2100.
Impact on Occupant Comfort
Now that we have seen three key external factors impacting buildings, let’s take a look athow the occupants could be affected by climate change.
1. Indoor Air Quality (IAQ)
When common indoor pollutants are understood and controlled, the risk of indoor health problems is reduced and the quality of work and comfort of employees are improved.
One way of measuring the indoor air quality of a roomis to measure its airCO2concentration. This can be done using Dexma Analyse as explained inthis article focused on indoor air quality.
IndoorCO2levels are usually higher than outdoor air ones,due to theCO2exhaled by building occupants and produced by some building appliances, like gas stoves for example. Therefore, a common rule of thumb is to try tokeep the IAQ below 800 ppmwhere the air quality standard is considered “fresh” and “normal”and to absolutely avoidCO2concentration above 1200 ppmcorresponding to “serious pollution” directly affecting health.
The easiest way to reduce theCO2level is to guarantee adequate ventilation and thus exchange “polluted” indoor air for, usually, cleaner outdoor air.勒t’s simulate the scenarios 2000, 2050 and 2100 for our office model and evaluate how climate change affects the IAQ.
As we can see on the graph, the results display that the IAQ in 2050 (middle column) will slightly deteriorate compared to 2000 (left column), while it will significantly worsen in 2100 (right column), reaching 1200ppm in a dark orange hue. The perfectly sized ventilation system will keep the indoor air quality below 800ppm for the whole year 2000, while the 800 ppm threshold will be crossed during 1363 hours (52% of occupancy hours) and 2610 hours (100% of occupancy hours) for the years 2050 and 2100, respectively.
Dexma Analysewill be of great help in monitoring yourIndoor Air Qualityin terms of indoor CO2, temperature and humidity and in creatingbetway 365客户端
for evaluating the effectiveness of your energy-saving measures.
2. Thermal Comfort
Due to the multitude of factors and its “subjective” nature, thermal comfort is usuallyhard to measure. A way of approximating it has been established in the 1960s by the Danish professor Povl Ole Fanger and is called the Predicted Mean Vote index (PMV). This index is based on the “perception of a large group of people”.It predicts the average vote of a large group of people on a seven-pointthermal sensationscale. This prediction takes into account all the following parameters: Metabolic Rate, Clothing Insulation, Air Temperature, Air Velocity, Mean Radiant Temperature, and Relative humidity.
这是模拟2000年度PMV指标, 2050 and 2100 for an open space from our office model. The open space indoor temperature is maintained between 22ºC and 26ºC during working hours (8h-18h)thanks to its HVAC system.
Thus, with a building perfectly air-conditioned, the indoor thermal comfort will only slightly be affected by climate change from a thermal comfort point of view.
勒t’s think about another scenario where we remove the cooling systems from our model. What would happen ifthe only possible way of cooling down the office space would be to manually open the windowswhen it’s cooler outside, which is still the case for some office buildings nowadays?
Well…the results demonstrate a big increase in overheating hours (PMV > 1), from 230 hours in 2000, to 380 hours (+65%) in 2050, ending with 525 hours in 2100 (+128%). In other words, it shows thatmanually cooling an office room(by opening the windows) is very likely tobecome impossible in the future, even in temperate climates.
3. Indoor Air Humidity and Temperature
Another way of measuring thermal comfort would be tomeasure the room’s relative humidity and temperature throughout the year. Relative humidity between30% and 60%and a temperature between21 and 26ºC往往被认为舒适的办公室。勒t’s plot the room relative humidity vs temperature for an open office space for 2000, 2050 and 2100 in apsychrometricchart. The green box you see representsthe comfort zonewhereas the crosses representthe interior airthroughout the year.
In this sense, we can see an upward shift in the relative humidity.Indoor comfort issues will very likely shift the winter dryness problems towards summer humidity problems.
4. Impact on Energy Consumption
To analyse the building behaviour from the point of view of theheating and cooling energy consumption,我们将比较在另外两个构建在里昂climates: in Oslo and Sevilla.The building fabric, especiallythe insulation thickness and the window thermal transmittance, have been adapted to the corresponding meteorology for giving more realistic results.
From the graphs, we can deduce thatthe cooling energy will increase while the heating energy will decrease in every case, which was foreseeable. An office building’s totalenergy consumption would decrease in cold regions(e.g. Oslo), or stay constant in temperate regions (e.g. Lyon), but will very likelyincrease significantly in hotter regions(e.g. Sevilla). Temperate regions where the focus is currently the heating energy consumptionwill slowly shift their attention towards cooling energy consumption. This may also bring the need fornew energy efficiency measuresfor the built environment.
To sum up, in this article, we analysed office building behaviour for three scenarios: the years 2000, 2050 and 2100. The focus was put on theIndoor Air Quality,Thermal Comfortfelt by the occupants, theIndoor Air TemperatureandRelative Humidity, and the Building HVAC Energy Consumption.
The results showed that the future could be atrade-off between higher energy consumption and a comfort decrease. This means that a generalrethink of the way we plan, build and operate buildings will probably be needed.
As part of this plan, theconstant monitoring and improvement of your buildingswill become more and more important. In order to reduce the impact of climate change on your building,Dexma Detectwill be useful to evaluate your building’s efficiency so that you can implement improvements.
In addition,我们的报道tool can provide you with precious information about your energy consumption, in a form that you can understand easily and use as a basis for taking relevant and clear action toward greater energy efficiency. Learn more aboutDexma Dashboards here.If you feel ready to embark on a new journey, or if you need more information, don’t hesitate toget in touch with our experts!
Editor’s note– This article has been written by a leading expert in energy management software:
Johann Loux,Building Energy Modelling & Data Scientist Engineer, part of the Dexma Detect team since 2021. His objective is to improve Dexma’s AI algorithms through automated energy modelling of buildings. He also brings his expertise in the field of energy efficiency to the development of Dexma’s products.
