Here are some feedback questions from chapters of "Heating, Cooling, Lighting: Sustainable Design Methods for Architects"
1.1 Explain how the history of vernacular and regional architecture relates to energy performance.
In ancient times, buildings were constructed to shelter inhabitants from their climate. They built on necessity to manage the sun, rain, snow, and wind. They also found ways to heat, cool, shade, and light these areas to improve upon interior comforts. This led to regional vernaculars, in which, buildings exhibit design features specific to their climate. Ultimately, designing a structure to work with the climate minimizes the need for auxiliary mechanisms to establish a suitable interior environment. Building with region-specific design techniques in mind will allow for higher efficiencies in energy consumption without sacrificing comfort.
1.2 What is the 3 tiered approach and what are the benefits of following it?
The 3-tiered approach to the sustainable design of heating cooling and lighting includes: Basic Building Design, Passive/Natural Systems, and Mechanical Equipment.
Tier 1 suggests that the most effective energy reduction technique is through Basic Building Design. The idea is that with proper design decisions, the energy requirements of a building can be reduced by as much as 80%. Our goal is to effectively perform heat retention, heat rejection, and heat avoidance through proper location, orientation, materials selection, window placement, and efficient appliances. Tier 2 will utilize Passive Systems, including direct gain glazing, thermal mass, comfort ventilation, and natural lighting techniques to achieve additional heating, cooling, and lighting needs of a building. Any additional comfort needs should be met with mechanical equipment such as heat pumps, space heaters, air conditioners, and task lighting. Preferably these devices will be powered by capable renewable energy sources.
1.3 What is passive survivability and how does it relate to sustainability?
Passive Survivability is the ability for a building to continue to provide shelter for its inhabitants despite a severe situation. Be it a hurricane, blizzard, tornado, earthquake, or power outage – a building is should have a certain level of survivability to withstand the extreme and unpredictable occurrences in nature and protect its inhabitants in times of need. A building with higher survivability may also have independent systems capable of providing electricity or potable water for its inhabitants during a time of need.
1.4 In what scenarios is your design vulnerable with regard to passive survivability? What changes could you make to your design to improve its passive survivability in these scenarios?
Our design has a lot of windows, so it is susceptible to heat loss through these surfaces. This equates to a reliance on heating or cooling during extreme instances. It’s possible a blizzard could cause a power outage and the solar panels could become covered with snow, making the house susceptible to the cold. Also windows are less structurally sound than walls and would present a vulnerability during hurricanes, tornadoes, and earthquakes, although these are unlikely in our climate regions. If we incorporated battery storage for our PV panels we could support our radiant heating systems during a utility power outage. Also, if we had designed a basement, we could establish a secure below ground shelter that would protect its inhabitants during any crisis.
2.1 How would you respond to the following question from a client: “how do you incorporate sustainable design considerations in your work?”
The sustainable design considerations that I incorporate include climate responsive house that are highly efficient and produce minimal waste. My goal as a designer is to incorporate as many natural and passive techniques for heating, cooling, and utility usage such that you house is easy to maintain and maintains comfort. By designing a building with the highest efficiency rating, I can ensure that it will produce a minimal amount of waste and will require the least dependency on electric and water grids.
2.2 What is embodied energy and to what degree will you consider it in your work?
Embodied energy is the amount of energy used in the procurement of raw materials, the production of that material into usable goods, and the transportation of that good to the consumer. It will be very important for me to consider embodied energy when sourcing materials. Local materials exhibit the best opportunity to minimize the embodied energy. Also, the prefabrication of building sections and recycling existing building materials can limit the amount of energy wasted during construction.
3.1 Explain how different aspects of your design are responses to an understanding of the 3 different forms of heat, sensible, latent, and radiant heat. (The more ways you list the more points you get)
Our design is heavily influenced by south facing window glazing which allows for the direct gain of heat from the sun’s rays. The windows establish a green house effect by trapping the long wave radiation of the sun inside the house. The result of this is direct gain sensible heating within the house increasing the overall temperature. All of the objects within the house absorb the suns radiation and will radiate heat when the air temperature is less that their surface temperature. The heat from the sun’s rays is also stored in the thermal mass of our concrete floor and structural elements of the house allowing for a time lag radiation of heat. To supplement natural heating in the winter we have radiant floor heating, in which the sensible heat of water in coils radiates through a thermal mass (concrete, wood) to increasing the room temperature.
We also utilize cross ventilation window system which effectively takes latent heat out of our humid climate by flushing the high water content air to the outside.
3.2 Explain how latent heat could be used to improve a buildings performance.
Latent heat can be utilized through evaporative cooling. By providing a source of water at the roof of a structure, the resulting system will allow the water to absorb heat from the air in the form of latent heat which either causes the water to change to steam, or will be reemitted to the cooler outside air.
Another instance we discussed in class is that of phase changing walls. In this case, the wall material would absorb the heat of the room, but the material would not heat up, but rather store this as latent heat in necessary to implement some sort of phase change of the material when enough heat is absorbed.
3.3 What are the different energy transfer mediums commonly used in HVAC design? Which ones are you using? Why did you select them?
For HVAC systems the common mediums of heat transfer are Forced Air, Electric Resistance, and Radiant Water. Each has different qualities, pros, and cons. Forced air is effective in both heating and cooling spaces quickly, however it requires large ducts. Electric resistance heating is good for localized and immediate heating, although it lacks efficiency. Radiant Water heating is compact, quiet, and efficient. We chose to use radiant water heating through our entire house. We use radiant coils in the concrete slab of our foundation to provide radiant heating to the entire ground floor. Also, we will run the hot-water supply to the second floor to and use the Warmboard product as a distribution method. Using radiant water heating allows us to use the hot water supplied from our heat pump and also allows for us to use solar collector panels to heat water, if desired.
3.4 Does your design use natural convection as part of a passive strategy? If yes, how? If not, how could you incorporate it?
We have a lot of thermal mass in our foundation which acts as a heat sink and will absorb heat during the day and radiate heat in the evenings. This radiated heat will be naturally convected through the house, as warm air naturally rises. We can speed up the convection process by opening our clerestory windows improving ventilation. By creating a draft through the house the thermal masses can dissipate their heat energy through convection more quickly.
3.5 What is a heat sink?
A heat sink is a material that stores and dissipates heat. When the outside temperature is higher than the material temperature it will absorb the heat from the air, effectively warming itself up. When the outside temperature drops, the heat sink will then dissipate its heat to the surroundings.
3.6 Explain how different aspects of your design are responses to an understanding of the Transmittance, absorptance, and reflectance. (The more ways you list the more points you get)
The solar radiation of the sun’s rays will transmit through our large south facing windows during the day. The windows admit short-wave radiation and block long-wave radiation from leaving. Our radiant floor heating the concrete mass will act as a heat sink to the daytime sun. In this case the radiating sun rays are absorbed in the concrete and converted to sensible heat – as the temperature of the slab will increase. There will also be an amount of radiation that is not absorbed by the floors/objects in our house. This radiation will be reflected and dispersed onto other objects in the house.
3.7 When and why would you use the concept of time lag as part of a thermal resistance strategy?
Time lag is a great feature when a large thermal mass heat sink is available. Tombre walls and water towers are such masses that are able to store excess heat in the room during the day and dissipate the heat during the night when the surrounding air temperature has dropped. This delay of heat dissipation is critical in keeping a house cool during the day when it is hot outside and warm at night when it is cooler outside.
4.1 Draw and annotate a psychrometric chart:
5.1 How would you respond to the following question from a client: “how and when do you micro climate considerations in your work?”
Microclimates are important for particular sites that may have unique characteristics different from their regional climate. Factors such as elevation, orientation, and proximity to bodies of water and manmade structures will be subject to unique patterns of temperature gradients, winds, and precipitation. For instance, a lake house may be subject to off-shore winds that would uniquely provide cross-ventilation, or erroneously suck the heat out of the house in the winter. The effects of microclimate must be considered prior to the design.
5.2 What is the urban heat island effect?
The heat island effect is an occurrence in cities, in which all of the man-made structures contribute to a higher annual temperature. The mass of buildings, streets, and parking lots effectively warms a city’s microclimate. City temperatures are about 3 degrees warmer than rural areas in the winter and 7 degrees warmer than those same areas in the summer.
5.3 Describe your approach for dealing with the 2 different climates you selected for your design.
Our climates include Boston, MA and Aspen, CO. Both are cold climates which present particular challenges with heating and proper orientation of windows. The differences include the humidity levels, in which Boston is very humid, while Aspen is quite dry. Also, the amount of solar radiation varies between the two climates which will contribute to different heating/cooling effects. The yearly temperature swings are greater in the Boston area than in Aspen, so it is important to have the ventilation cooling available. We felt that radiant heating would be effective in both climates, and that the performance of our thermal mass will maintain comfort throughout the seasons for both climates.
6.1 How are you sizing the southern sun shading devices? Where are you getting your dimensions from?
Our site latitudes are 42.36 and 39.19 for Boston and Aspen respectively, so we were able to size the same overhang for each. Because both climates are considerably cold, we chose to use the ½ rule for designing the southern overhang of our roof, instead of blocking out the maximum summer solar radiation fully as is customary in hotter climates. Our calculation is such that it the south facing windows are subject to ½ of available solar radiation on the Summer Equinox. These calculations yielded overhangs of 1’-4.5” for Boston and 1”-1.5” for Aspen. For simplicity, we chose an overhang of 1’-3” for our south facing roof for both regions.
7.1 What passive solar concepts does your design employ?
Our design focus was on heat retention. We have ample southern exposure that is subject to the direct gain effects of the winter solar radiation. Also the design of the south facing overhang incorporates the different incident angles of solar radiation through the course of a year. Therefore, we will be blocking most of the sun’s rays from the direct-gain effect during the summer months. The slope of our roof is oriented south for optimal collection of solar radiation for heating and electricity needs.
7.2 Explain why your design is smart with regard to lighting.
By incorporating a lot of windows, we can limit the daytime electric lighting demand by utilizing daylighting. For the night time, we have incorporated general and localized lighting strips that will provide adequate illumination levels for each region of the house. Also we have provided ample interior outlets to allow the homeowners to set-up task lights to fit their demands.
8.1 What would you consider in determining if active solar systems are a good idea for a particular project?
The most important consideration is the orientation of the roof, both direction and slope. If the roof is with 15 degrees of south, it should provide an effective surface for mounting solar panels. It is a rule of thumb to tilt the panels as close to the latitude of the location as possible. Also consider any shading features like trees or buildings that may inhibit the amount of incident solar radiation. The sizing of the solar panel array will depend on the regional weather patterns of sunny days and should correspond to the expected electricity demand of the appliances or hot water demand of the homeowners.
8.2 What would you say to a client that asked what are the difference between solar thermal collectors and photovoltaic panels? When should I consider when using either?
Solar Thermal collectors use solar radiation to heat a water supply. They are most effective in hot water applications, such as hot sanitary water for sinks, washer, and dishwasher or for heating a pool. On the other hand, Photovoltaic panels are most effective in turning incident solar radiation into DC electricity. This electricity can be used to power as much of your appliances as the source allows. Also excess electricity from the panels may be stored in batteries or distributed back to the grid.
9.1 What sort of shading devices are you using in your design?
The south facing overhang will be effective in shading during the summer. We compensate for additional shading needs we will use simple blinds and window covers. This will allow the homeowners to adjust the amount of sunlight into their house per their desire. This allows flexibility and customization that is hard to match in other shading techniques.
9.2 What other type of devices would also work? What is the reasoning behind the method you chose?
We could also have incorporated overhang awnings, rotating louvers, or deciduous plants to assist with the shading needs of the homeowners. As I mentioned above the flexibility and customization of simple blinds on each window is unmatched in other movable and permanent shading devices.
15.1 What are the differences about the 2 different thermal envelope details you designed for your project?
We designed for a slightly high thermal resistance for our Aspen profile. For Aspen, we incorporated an Exterior Insulated Finish System (EFIS) wall construction. This system utilizes a stud wall with fiberglass insulation between the studs, 4” Expanded Polystyrene (EPS) exterior insulation, and a stucco exterior finish. For Boston, we will use Structural Insulated Panel (SPI) wall construction. This system utilizes an EPS insulation core with fiber-cement cladding panels. This construction provides less thermal resistance than does our more robust Aspen construction.
15.2 Use the equation in Sidebox 15.2a to compare how your 2 different wall sections would work in the most extreme conditions of the colder of the 2 climates you selected.
15.3 List and justify the different types of insulation you are using in your different thermal envelope designs.
We are using a combination of fiberglass and EPS insulation for the walls of our house and spray-in foam insulation for the roof. The rigid EPS insulation is effective and durable. Fiberglass works best for stud-wall construction, while Spray-In makes roof installations easier to manage.
15.4 Thermal bridging can hurt building performance but is unavoidable at times. What parts of your design are the most vulnerable to thermal bridging and what have you done to minimize the damage done by it?
The clerestory windows in our house provide the opportunity for ventilation and daylighting, however, they are also susceptible to heat loss through transmission and infiltration. We need to ensure that they are properly installed and sealed and that they are completely shut during the cold winter months. We have east, west, and north facing windows that also act as thermal bridges. We recommend proper window coverings to provide additional thermal resistance and reduce the heat losses through these surfaces.
16.1 Describe and justify your choice of HVAC systems.
We chose to use a Heat Pump to provide all the hot-water heating needs of our house. This allows us to deliver potable hot-water and water for radiant floor heating from the same device. A heat pump is efficient and less uses less energy than a conventional boiler. We also have incorporated clerestory exhaust fans for ventilation and cooling when the need persists.
Summary: South Facing windows, Radiant Floor Heating, Thermal mass heat storage, Clerestory exhaust fans, EPS insulation, Heat Pump, South Facing Roof