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Green, green and green

March 28, 2010
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Things that are green:

  • Plants, as in growing plants on the roof that will insulate our building and provide us with a place to garden.
  • Sustainability, as in roof and HVAC systems that limits the energy footprint of a BAB.
  • Money, as in the limited amount of cash we have to do all the work needed.

Now that our little house has sold, we know how much cash is available to us to get this project rolling! Our first construction project is a combination of the roof replacement and the HVAC system. Both are currently completely lacking. They also represent a huge upfront financial investment, as well as work we can’t DIY. Though uncomfortable, we could move in without having heat and cooling, but if we come back later to install it, we’d need to rip out some portion of the replaced roof. We’ve decided that the most cost efficient path is to do these projects concurrently.

Our yard?

The choices we make on one system impacts the other. The roof systems we are considering provide different levels of insulation, which affects the scale of the HVAC load. HVAC systems take up different amounts of roof area. Plus, the more of our budget we put into one or the other of these components, means less money available for the plethera of other projects in our future. We are considering everything from standard forced air to photovoltaics and solar thermal. The decision will come down to initial costs balanced with operational costs and fit with our desired roof top activities.

A note about standard ‘flat’ roofs. A membrane roof is considered the best choice for flat roofs these days. There are different types of membranes and installation systems available. For these products to be installed with a valid warantee, however, there needs to be at least a slope of 1/8″ in a foot. To add the slope to our pond-like roof, the standard choice is tapered insulation. Unfortunately for our situation, tapered insulation is beaucoup bucks. To further complicate things, we have one internal roof drain for the 6,500 sf of roof area. We figured that, at the point furthest from the drain, the insulation would be almost 2 feet thick. That is great insulation value, but not great on the pocket book or the kind of yard we can get excited about. The alternative is to install addtional roof drains. This is not difficult, given the clear space below the roof, but would add to the overall cost of the system.

We know we want to use the roof as our ‘back yard’ and garden, so planting the roof  seems like an obvious solution. There are many benefits to a green roof that have nothing to do with gardening. They are so cool infact, the City of Chicago has established a very successful grant program to encourage the installation of green roofs. In our situation, a green roof could provide great insulation, it doesn’t require us to add a slope to be warranted, it offers terrific environmental benefits and we don’t need additional roof drains. 
The downside? Cost, of course. The system we looked at that has been installed locally, is about twice the budget pricing of a typical membrane roof.
The next post will cover the green roof system we’ve been investigating.
One Comment leave one →
  1. Dan Mitchell permalink
    March 29, 2010 7:29 am

    I’m sure you guys have looked into any potential credits or tax savings for use of photovoltaics. I have been investigating the impact of a ground mount system out in Colorado and there are some really good incentives from both the local utility company, state and feds. Of course my square footage is a “little bit” smaller so my KW demand/usage is between 3 and 4 KW. Put the better system in now, as you can’t turn back once its done. Glad you are doing it and not me!! Good luck.

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