Climate-based Design

We hear so much about climate change in the news, and it seems to be characterized as a global phenomenon. But the climate, which is the accumulative history of trends in weather patterns, varies greatly from place to place, even with the macro-changes that are occurring. In fact, there are more than seventeen different climate zones in the world! Beyond the seventeen classified climate zones, which are defined by the Koppen Geiger climate system, there are nuances with each micro-climate or hyper localized conditions. The characterization of a climate is influenced by more than 50 variables, including temperature, humidity, radiation, cloud cover, wind, rain, and numerous other factors.

So how do architects respond to climate in the way they design buildings? If you imagine yourself standing in an open field that is sunny and hot, think about what you would be wearing – probably a light t-shirt and shorts and perhaps a large-brimmed hat to shade your face. Now, imagine that a lake appears in front of you and the heat of the sun begins to cause evaporation off the lake’s surface causing the humidity to increase drastically. You pull out a handheld fan and begin fanning yourself to keep cool. Soon enough, clouds begin to roll in and the temperature becomes cooler, you may want to put on a long-sleeve shirt and jeans and no longer need the hat so you can get some daylight exposure to stay in a decent mood. Soon, the clouds become heavy and dark, and it begins to rain. Well, you put on a raincoat, which has a hydrophobic finish, and you open an umbrella with large surface area coverage to keep yourself dry! Now, the temperature is continuing to drop while it is raining, and soon enough the conditions turn to snow. Because you are trying to stay warm, standing exposed in this open field, you remove the raincoat and put on a heavy, well-insulated winter coat and a wool hat to retain heat within your body.

Designing buildings for different climates is a lot like choosing the appropriate wardrobe for the weather conditions. In hot dry climates, we need to shade the building surfaces as much as possible with large roof overhangs (think large-brimmed hat). In hot humid climates, we need to encourage ventilation and airflow in and around the building to keep things cool. In temperate overcast climates, we need to provide large bay windows to allow access to natural daylight. In rainy climates, we need to keep water away from the building structure, so large roof overhangs (like an umbrella) and hydrophobic cladding materials are helpful. In cold climates, we need provide lots of insulation in the exterior walls and roof to prevent heat from escaping the building interior. Each of these strategies is quite comparable to the clothing you might choose to wear in the varying climates. 

Complexities in building design arise when we deal with more varied climate conditions, such as seasonal changes that give a wide range of temperatures and humidity. There are also more complexities arising with climate change phenomenon due to uncertainties and irregularities from traditional weather patterns as well as increasingly radical events, such as hurricanes, droughts, forest fires, and other natural disasters. Designing buildings with all of the climate variables and potential climate events in mind can quickly become a complex task requiring sophisticated and educated responses. However, putting the natural disasters aside, there are some basic rules of thumb that can help guide the homeowner with an understanding of how their house should be properly designed for their climate location and the seasonal variations.

It is wise to begin with the extreme conditions that might occur to establish the basis of design for the exterior walls and roof, or what is known as the enclosure system. In order to identify the extreme conditions within a climate that has seasonal variations, architects and engineers use a method known as degree day calculation. To calculate degree days, we first need the typical year of hourly temperature data for the location. Anyone can freely access typical meteorological year (TMY) data through the Department of Energy EnergyPlus website, but it doesn’t come in a format that is readable without other software. You can also find other readily available historic climate data from numerous weather sites online, or otherwise find resources online to calculate your degree days for you. I find the BizEE Degree Days online calculator to be a great resource for this purpose. You just enter your zip code, then identify the weather station that seems to be in closest proximity with your location and a degree day file will be generated for you.

But what does this degree day information indicate and how is it calculated? There are two types of degree day calculations – one is for determining heating degree days (HDD) and the other is for determining cooling degree days (CDD). In both cases, an acceptable temperature for thermal comfort is established as a baseline (i.e., 65^oF for a heating season and 72^oF for a cooling season). In heating degree days, any hourly temperature below the baseline will be considered in the calculation. In cooling degree days, any hourly temperature above the baseline will be accounted for. Once we have the baseline established, an accumulative calculation is run for adding each “degree” below or above the baseline through summation. Keep in mind that on some dates in the year, we may have both heating degree and cooling degree hours during the 24-hour cycle. Ultimately, the results will indicate how many temperature points below or above our heating and cooling baselines we have for a given time period (we can run these seasonally or annually). To start to understand the overall conditions for your location, it is best to review the annual results. Some climates will indicate a greater number of heating degree days, which means that keeping your house warm and designing for cold conditions is the primary goal. In other climates, the cooling degree days will prevail, meaning that designing the house to keep the interior cool will be the primary goal.

There are a handful of design strategies that allow for natural heating and cooling before we would have to depend on active mechanical systems. Many design strategies are dependent on the orientation and geometry of the home with relation to the sun and its solar path at the given latitude and longitude and elevation. Other design strategies are dependent on the materials selected for the enclosure system and the composition or layering of these for different thermodynamics. All of the design strategies that can be employed will assist with maintaining adequate interior thermal comfort for human health and reduced utility bills. A range of different climate-based design strategies will be explained in future blog posts, as each one is nuanced and requires detailed explanations. 

However, for some initial ideas, it is always helpful to take a look at early examples of vernacular architecture from your region. Traditional architecture (pre-20^th century) was almost always designed for natural heating and cooling to the extent possible with available techniques and methods of the time. The orientation and geometries of structures were appropriately sited to take advantage of solar heating and shading for cooling. Fenestration patterns of operable windows were designed to maximize natural ventilation and natural daylighting. And materials were employed to resist specific weatherization and heat transfer conditions of the region. The houses constructed during the period before mechanical heating and cooling systems were introduced are great examples of climate-based design.

Today, it is more difficult to see the evidence of climate-based design in houses, which can tend to be similar in form, not related to any specific solar orientation, and similar in material compositions, regardless of climate location. This is primarily due to the expansion of mass production with specific building techniques and the dependencies on mechanical heating, cooling, and ventilation systems. Always keep in mind that the more your house is synchronized with its climate through the design, the better equipped you will be to keep utility costs low and to improve your health and wellbeing.

If you are interested in more information about designing or renovating your house to optimize for your climate location, reach out to Designing WELL today for a group or individual consultation.You can always find more information and healthy home resources at Aletheia Ida Design and Architecture, LLC (AIDA, LLC) at www.aletheiaida.com.