Passive Design
Finalizing Floor plan
This week we received feedback on our initial ideas for our floor plans that we had created. Darren had pointed out that we all really needed to think outside the box a bit more, this is a concept house and we really need to show off all we have learned throughout the model and the weeks that passed. My floor plan I had came up with now seemed a bit boring and traditional after receiving this feedback. The porch i had added to my floor plan was a passive house principle but was not executed correctly, there should be a wall separating the porch from the main hall in the house to allow people to transition into the home, keeping the hot air in. The house did not seem to use its space efficiently, I had halls for the sake of having them, windows where I would not need them, and the overall area of the house meant there was more surfaces for heat to escape.
With all these points from my feedback in mind I realised I was going to have to completely reimagine how my house was going to be laid out inside. I really wanted to address more passive house principles so I began re-reading the Passivhaus designers guide, 101 rules of thumb for low energy architecture and the article recommended to us on Passivehaus plus about good form.
Rule 8
For my design Solar gain was always going to be my main focus seeing as my own home gains allot of its energy from the sun and its south facing windows. The kitchen and living space is south facing is by far my favourite room in my home, because of its large windows with unobstructed views, the warm summer sun, and the open plan living complimented by its higher then normal ceilings. Rule 8 shows a fantastic way of regulating over heating for rooms such as this, keeping them cool in the hot summer months and warm in the winter. By using large overhangs or wooden timber slats known as a pergola to partially block out the high sun in the summer months but allows the low winter sun in, these are permanent features which do not have to be manually operated like blinds making them more efficient. Below are some examples that I hope to take inspiration from in my design.
Rule 14
As you are well aware from the Google images of the site in last weeks blog, there are trees surrounding the site on both the south and west. Most of these trees are all deciduous meaning they will lose their leaves in the winter months allowing 70% of the suns energy to pass between the branches. The few evergreen trees that are there will either have to be trimmed back or cut down depending on their size. In the summer months the trees will provide shading for the house to prevent over heating, these are quite large trees but they will still not block out the entirety of the suns rays as shown by the diagrams above.
My original plan was to cut down all the trees on the south side, to allow the sun to shine through, but now I believe they will just need to be trimmed back so not to cause damage to any of the buildings by falling branches in strong winds or bad weather. The trees will also provide shelter for the dwellings keeping strong winds off of the south and west facades. Here is an image of the different trees on the site from Google maps, as you can see there is also allot of shrubbery which is going to be trimmed back to maximise space on the site.
This is a passivhaus principle I really tried to use in my first floor plan which is clear by the large separating wall between the hall/bedroom to the living/ dining kitchen space. The highly occupied rooms that require the most heat like the living room and kitchen should be south facing and rooms such as the utility and bedrooms should be kept to the north of the building. Since I plan on having semidetached houses this means each building will be the mirror image of the other, so the East wall of one house will be the west wall of the other, and vice versa. I will have to come up with a clever layout design that will be easily mirrored so that both units will have the same solar gain and not have one dwelling that works better then the other. The large open plan living area like in the image above is also something I hope to incorporate into my design.
Rule 41
The difference between insulation and thermal mass was something I was aware of, but thought it was either one or the other you would have to chose when it came to the envelope of your house. This made me rethink what my initial plan for my wall and floor details would be, I had planned on going with a timber frame construction as they are far easier and faster to insulate when building, compared to a block wall. In saying that, sometimes compromises have to be made in order to achieve what you want in your design, which is why I am now more drawn to having a large block wall, so that the build is well insulated but also has a large thermal mass, removing the need for a heating system in the home. Another thought that came to mind was instead of having tiles or timber floors, perhaps a polished concrete floor would be a better choice since concrete has such a large thermal mass. It would mean come the evening time the heat it has stored throughout the day will slowly be released, rising from the ground up keeping the home warm well into the evening.
Similar to what I said above about the heat energy rising from the concrete floor, that energy heats the air which heats the home. That warm air will try to achieve equilibrium with the cool night air outside which is why having such a large wall on the south side with insulation and triple glazed windows will prevent this heat energy escaping. One thing I have been looking into is having a slanted ceiling to guide the warm stale air that has risen up towards the vents in the roof to extract the stale air which I will talk more about below, and the use of an MHRV system. This is another reason why open plan is a big thing for me in my design the warm air will be encouraged to move to the cooler spaces of the home, if there is nothing obstructing this like internal walls or doorways the space will be warmer as a whole and you will not be cold in one area of the home and to warm in the next. Trying to organise my open plan space is something I will have to get just right and below are some images which I have taken inspiration from.
The large glass doors and windows, the breakfast bar, how the have somehow separated living, dining and kitchen while having them all contained within one space is something I hope to achieve in my floor plan design. How the ceiling slants up in one direction allowing for these large high ceilings making the rooms appear much larger then the actually are as well as directing the air towards the MHRV vents which I would have installed in my design.
Rule 61
Above I had mentioned a MHRV system a few times, it is an essential for achieving a passive house design. By fully insulating the external envelope of the building and having no ventilation you would be living in a plastic bag, which is why an MHRV system is introduced to the dwelling. It allows the stale air and CO2 to be extracted from the home and replaced with fresh air while retaining the heat the stale air was carrying, insuring every bit of heat energy that has been gathered throughout the day has been maintained. In the Above image you can see how the slanted roof guides the air up towards the ventilation system, while in summer the slanted roof also prevents over heating by allowing the heat to rise up and escape.
Passivhaus Plus Good Design
The short article by John Hearne highlighted a few key issues I myself would face when it cam to the design of my houses and the layout they would be in, to maximise solar heat gain. I must try and fit 12 houses into such a small area, johns article highlighted how another designer overcame this problem.
"Pressed by density requirements on one side and delivering the right orientation on the other, one of the central challenges facing passive solar estate design is overshading. Smart design has however managed to meet this challenge even on the tightest, most restricted sites. Philip Crowe cites BedZED, the Beddington Zero Energy Development in London. Powered only by renewable energy generated onsite, the development incorporates some 777m2 of solar panels and makes maximum use of passive heat." (Hearne, 2019)
Through clever design they carefully planned out the orientation and layout of their homes, by having the living spaces to the south, while having the work spaces to the north, which would be my bedrooms/ study area for the mature students. The daytime workzones tend to have higher cooling then heating requirements so by placing them on the north reduces energy demand, the article also stated that the "lack of glare in north light makes it excellent quality light for working." (Hearne, 2019)
The article also highlighted the benefits of different roof patterns, and how "terraced housing with a sawtooth roof pattern, rather than the familiar continuous ridge and eave formation, can also defeat overshadowing issues and orientation for solar systems." (Hearne, 2019) These sawtooth roofs are something I really hoped to incorporate in my design as the are slanted roofs, but also allow light in through them at particular angles.
My Final Floor Plan With Passivhaus Principles
Saw tooth roof, lighting and air circulation – the purpose of the saw tooth roof here is to allow the sun to hit the central wall of the house, this wall will hold the heat late into the evening and will also reflect light onto the landing, stairs, living and dining area. It also lets the stale air to rise up to MHRV ducts giving a nice circulation of air in the house. The lighting of the main living spaces is shown by the sketch on the right. Seen in image below.
Airtightness – In order to keep the heat the entire house will be wrapped in an airtight membrane to keep warm air in and prevent moister or vapor getting in causing mould.
Overhang and slats to prevent overheating – In the image on the right you can see the drastic overhang on the roof to prevent overheating in the summer months and the timber slats preventing some of the sun reaching the downstairs windows. Seen in image below.
South facing open plan kitchen and living area - This is the main area in which the residents will spend most of their day so I have made it as open bright and airy as possible with maximum solar gain and open plan design with less surfaces to heat meaning the large floor space can hold the heat energy and distribute it evenly come the evening. Seen in image below.
Linked to upstairs living area – I decided to double the living space by splitting it making good use of unused space above the kitchen, so it is two separate areas all in one open plan room. Seen in image below.
Compact building form – the buildings rectangular shape means there is less surfaces for heat to escape from and less chance of thermal bridging occurring. As shown by the above floor plans.
Solar Panels - The blue bar on the image below represents where solar panel's will be located on the building, they will be essential for heating the dwellings water supply. Thermodynamic solar panels are a reliable heating system providing year round water temperatures of 52°and have a cheaper overall running cost while also being a more environmentally friendly option.
In order to better understand the shape and layout of the house, here are some concept sketches of the external dwelling as well as a north, south, east, and west profile.
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