House of the future

[Chris Stewart]

Here are some other ways it could be done. This addition only adds another 65 sq. ft.

[Chris Stewart]

The roof needs to provide all the hot water and winter heating and also harvest rain water.

It would be made out of Structural Insulated Panels (SIPs)

Directly above that would be a non permeable water barrier.

The roof would be metal.

In between the metal roof and the water barrier water would be circulated.

During the day this water would capture heat from the sun. In the summer only water for the hot water system would be heated.

In the winter water contained in the below ground cistern would be circulated and would store the heat so that it can be used to heat the home.

On cool nights in the spring and fall it could also be used to cool the water down to provide semi-passive cooling.

[Chris Stewart]

I was just reading an article about the "Katrina Cottages"

Here are many of the plans:
http://www.cusatocottages.com/

Some of these are much smaller than my current design and it made me realize that I am still thinking too conventionally. At 1212 sq. ft. this house still represents a high degree of luxury that many Americans can not afford.

So in my green subdivision of the future this last design will probably represent the luxury class home.

[Chris Stewart]

Well my first concept was to locate the cistern underneath the house. This would mean that you would need a pump and electricity to get water out of it.

The cistern would be used for all water needs except drinking water and also heat/cool thermal mass storage.

Now I am thinking of storing it within the living space. Either in a thick wall or vertical cylinder. This would allow the water to mostly be gravity feed to fixtures and also allow the thermal mass to be used without the need to pump it through an hydronic floor heating system.

I'll have to research cisterns some but I believe the water has to be treated to limit fungal growth (perhaps with chlorine like city water) so there could be issues with using it for thermal mass also.

Here is a house that uses water inside for thermal storage:
http://www.motherearthnews.com/Green...Wall-Home.aspx

[stew]

Love the way you think Chris, Few thoughts- the thing about storing water in the living space is that you will be paying property taxes on that space-- might not be a big deal but in my next home I want to try to keep those costs as low as possible. I have been thinking simlarly about the roof slope/ function and came up with the reverse of your solution-- ie a Gambrel style that puts the lesser slope further from the eaves-- maybe this is because I am in the north and there are snow load/cover issues to contend with. It also seems that the large low slope has more area with the sun beating down on it in summer which potentially adds to the cooling challenge- though perhaps the photovoltaics will block/reflect much of that. And in terms of sun-- isnt there a fair amount of heating needed in winter in TX-- seems like your design ignores solar gain- with properly designed overhangs south facing glazing can serve to let in free heat in winter only. I cant see why any home that needs some heating would not include maximizing solar gain in the heating season- and minimize north facing glazing.

[Chris Stewart]

You bring up a lot of good considerations that get a little hard o address in one post so please bare with me.

First of all let me say that I randomly picked a South facing location just to see what I would do in that particular situation.

My first ideas where to shape the roof in order to maximize orientation for PV and solar hot water. I found it hard to minimize the volume of the interior with that approach. I considered the fact that a one story house would have more exposure to the sun and that potentially a two story house has a better surface area to volume ratio.

My main thought on solar gain is that windows are difficult to control. At night they loose energy and sometimes even in the winter they can produce unwanted solar gain.

Also it is difficult to store large amounts of solar energy within the house. For example: in order to have enough heat available to go 3-4 days without sunshine you would have to get the interior of a house uncomfortably warm. A water tank holds heat energy which can then be released as needed.

I don't see property tax as an issue. This house is far smaller than the current average and so property taxes would be much lower.

The south facing roof is basically a solar water heater. I exchanged efficiency of collection with quantity of surface area. In other words- I could buy smaller solar hot water heaters and orient them better but I decided instead to make the entire south facing roof the collector.

My theory here is that it makes the roof less complicated not having additional panels attached. I wanted to collect rain water anyway and this roof makes it a relatively simple process. A metal roof would be more durable than glass panels.

[stew]

There was a time I toyed with the idea of 100% passive solar for heat and the issues of overheating, storage, and heat loss (and frankly glare- a room can be uncomfortably bright with a low winter sun angle and an entire wall of south facing glass) do create problems in that area. My current thinking is not to try to accomplish that. My thinking is just that since glazing is inevitable in any design for the sake of day lighting and the fact that no one wants to live in a windowless dwelling, the windows that are included ought to maximize heat gain in winter and there should be thermal mass indoors to store some of it. As it is I see houses with walls of north facing glass and garges on the south side and I just shake my head. No way would I put in sloping glass- I dont wnat to live in a hot house- but a decent amount of vertical glass with a properly sized overhang on the south face and minimal windows and or garage placed on the north side seems to me to be a basic requirement in cold climates if the site allows for it.

[Chris Stewart]

Yes, maximum passive or semi-passive efficiency makes many requirements which force us away from traditional design. In the future I don't see how we will be able to avoid it though. Oil, propane and natural gas will soon become too expensive for the average person. Some will be able to use wood but it isn't a practical solution for many.

As a designer I think it is fascinating that we can actually build a home that can be comfortable while consuming very little fossil fuels. But in all practicality we will have to wait for the cost of fossil fuels to push us that direction. I don't see that taking more than 30 years though considering the current rate of consumption.


I just read an interesting report:
http://www.austinenergy.com/About%20...ategicPlan.pdf

This is a power company in the nearby Austin, Tx. area. They are concerned about volatile gas prices, aging nuclear and other power plants, restrictions on the amount of pollution produced by coal fired plants and rapidly expanding population. They invest some in wind and solar but those sources are erratic and there is currently no way to store this type of energy.

For these reasons I believe it will be best for houses to be much more self-reliant in the near future.