Tag Archives: wish list

The green roof dream

design,

A vegetable garden on our roof has been on our wish list for a while. The question is if we can pull it off.

There are structural and budgetary challenges and they are closely linked. We have some very impressive steel columns supporting an equally impressive steel beam running near the center of the basement.

green-roof-structure-001

This assembly supports the interior load bearing wall of the 1st and 2nd floor and appears so sturdy that I was convinced it would support a green roof.

The actual roof structure, the 2 by 10 old growth joists running across the building, did not generate much confidence. I assumed this was the weakest structural link and would not support the extra weight of the airy vegetable plots.

green-roof-structure-002

How much structural reinforcement is needed? Are we talking about $500, $5,000 or $50,000? To find out, we need a feasibility study from a structural engineer.

I got Kerry from Louis Shell Structures (LSS) to take a look at the house and structures with me. He was very happy that I had all the walls open. He actually could look at and measure all load bearing components, which we did for about two hours.

To accommodate the vegetable garden, I assumed a growing medium depth of 6 inches and a drainage layer depth of 2 inches. All in all, a load capacity of 80 pounds per square foot (psf).

green-roof-structure-003

Kerry took all this information back to his office and began to crunch numbers–a lot of numbers! Lo and behold, the results were somewhat unexpected.

What I assumed to be the most solid component, the steel columns and beam, turned out to be a weak link. And what I thought to be the weakest link, i.e. the roof joists, appeared to be rather sturdy. Almost all roof joists are fit to support the additional 80 psf, with the exception of the long span area over the dining room and the kitchen.

green-roof-structure-004

Over the dining room area, I will need to sister the existing roof joist with two 2 by 10s (one on each side). Over the kitchen area, I only would need to add one 2 by 10 to each existing joist. All roof joists will need vertical blocking over the load bearing wall. And that is it for the roof structure!

green-roof-structure-005

As for the interior load bearing wall on the 1st and 2nd floor, we need to add some minor reinforcement. All typical door openings need a new 2 by 8 double header to transfer the load.

green-roof-structure-006

The larger opening for the French doors has to be reinforced with a double-LVL header (2 by 9 ¼ inches).

green-roof-structure-007

Some of the studs in the load bearing wall do not line up with the floor joists, which prevents proper load transfer. To solve this problem, we either need to add studs, or move the existing studs under the floor joists.

green-roof-structure-008

Last but not least, we have the unexpected weak link in the basement. It turns out that we will need to add a 4 inch steel pipe column half way between each existing steel column. The new columns will require a 4 by 4 foot concrete spread footing.

green-roof-structure-009

As for the budget, I think we are probably in the $5,000 range for these reinforcements. I am not sure when we will be able to put up the green roof. What I do know is that we should take care of the reinforcement now, while we have the chance.

Energy model

design, , ,

The road to a design workshop for our sustainable rehab took us to an energy model for the house (see also 09/09/2009 post). Our goal is to have a super insulated and airtight building envelop. But how much energy, CO2 emission and dollars will this save us and how much heating will we need?

I provided Corbett Lundsford from the Green Team Group with building floor plans and some building parameters that he input into the REM/Rate™ Home Energy Model:

Building shell:

  • Insulation of building shell: R-21 in 2×4 stud wall, 16 inches on center
  • Insulation of basement slab: R-5
  • Roof insulation: R-52
  • Windows: Double glazed, low E wood frame windows,  U-value of 0.25 and Solar Heat Gain Coefficient (SHGC) of 0.5
  • Exterior doors: Front door with U-value of 0.27 and all other exterior doors with U-value of 0.19
  • Infiltration: 0.2 natural Air Changes per Hour (natural ACH)

Mechanical equipment:

  • Heating: radiant heat (hot water radiators) with natural gas fired 90 AFUE boiler at 60 kBtu/h capacity
  • Domestic hot water: natural gas fired water heater at 0.63 EF with 30 gallon storage tank
  • Cooling: We decided against any air conditioning system, but would like to use ceiling fans and have a small window unit as a backup if needed. Over the past few years, we had a window unit in our un-insulated and drafty Elmhurst apartment. We may have used it three or five days in a year, usually when we had visitors. Knowing that we will now switch a very well insulated and airtight envelop, we don’t see the point investing in an air-conditioning system we won’t use.
  • Ventilation: Energy Recovery Ventilator at 300 cubic feet per minute (cfm) capacity and 250 watts

Renewable Energy:

  • Solar hot water: 128 square feet of evacuated tubes with 150 gal storage tank
  • Sun room for passive solar: Our enclosed back porch faces due south and offers the best and only opportunity for passive solar gain in the cooler seasons. We have the idea to create a ‘sun room’ with glazing on most of the south elevation, and awnings for shade in the summer months.  The infiltrating sun in the cooler months would heat up the building’s rear brick wall. We hope to use this thermal mass and energy to precondition air with which we would ventilate the rest of each floor.

Results

Corbett run three model scenarios for us, each with a slight modification to the above mentioned sun room:

Unconditioned sun room, full glazing

  • Design Load (kBtu/h): 53.2
  • Annual Load (MMBtu/h): 63.1
  • Annual consumption (MMBtu/h): 70.7

Conditioned sun room, full glazing

  • Design Load (kBtu/h): 52.3
  • Annual Load (MMBtu/h): 61.8
  • Annual consumption (MMBtu/h): 69.2

Conditioned sun room with ½ window sizes

  • Design Load (kBtu/h): 48.6
  • Annual Load (MMBtu/h): 57.3
  • Annual consumption (MMBtu/h): 64.2

I have to admit that I was surprise. I did not expect that bringing the sun room into the conditioned envelope would reduce our energy needs. In other words, heating the sun room will help us to save energy. Sounds somewhat counter intuitive, doesn’t it? That the reduction in window size would result in better efficiency was more intuitive, as windows are the weakest link in the envelope.

Here is another interesting result that adds to the feel good factor: Corbett compared our performance targets (outlined above) to those of conventional building performance levels. Lo and behold, we could save as much as $1553.00 a year on energy cost (and that is with current energy prices…).

Opportunities:

This energy model is by no means the final word, but provides us with a baseline that we can use for the workshop, design and decision making processes. I was sieving through the report details looking for opportunities and found them in the component load summary. This part of the report identifies how much energy (in Btu) is needed by or lost to various building components.

The single biggest energy loss is attributed to infiltration, in other words, having warm air leaking out of the building and cold air leaking in. This loss occurs at a rate from 28.8 to 30.5 MMBtu/yr., which is anywhere from 45 to 53% of the annual heat load! I like to think that this has opportunity written all over it if we take objective of a super insulated and air tight building envelope seriously!

What is:

ACH (Air Changes per Hour)

AFUE (Annual Fuel Utilization Efficiency)

Btu (British Thermal Unit)

EF (Energy Factor)

Low E (Low Emissivity)

R-value

SHGC (Solar Heat Gain Coefficient)

U-value

Dusting off the wish list

design, , , ,

We are anxious to start with the design, which will lead us to plans and specifications and ultimately to our green building permit. We have been deconstructing for a while to (hopefully) uncover all problems and develop an inventory of what needs to be fixed.

Interestingly enough, most problems we unveiled during deconstruction were water related: The damage to framing in the basement (see 04/23/2009 post), the jungle of existing and abandoned utilities (see 05/28/2009 post), water damage in the bathrooms (see 08/01/2009 post), a disintegrated roof drain (see 06/09/2009 post) and the mystery of the missing cold water line (see 06/22/2009 post).

We’ve begun to have a pretty good idea what the green rehab will involve. This is a good time to go back to basics – to revisit our project principles and take another close look at our wish list. I am talking big picture here, looking at the goals of resource efficiency and zero energy. I am not ready to get distracted by low flow water fixtures and LED versus CFL’s. Rather, I have to think about big ticket and building related items such as the envelope and energy sources:

  1. Super insulated and airtight building envelope, that helps us with reducing our heating and cooling needs. We intend to get away without central air conditioning.
  2. Solar hot water system for space heating and domestic hot water. We should be able to downsize the solar hot water system, because of the super insulated and airtight building envelope.
  3. Cast iron baseboard radiators for space heating. We are concerned about overheating the interior because of all the insulation and think that the small size of the baseboard radiators may prevent this.
  4. Biomass backup furnace for those stretches of overcast days in November and December when the solar hot water system needs some help.
  5. Passive ventilation systems to keep the air fresh and healthy in our airtight envelope.
  6. Heat recovery system for ventilation. We want the stale air out, but would like to keep the energy in (warmth or coolness).
  7. Sunroom for preconditioning. Our back porch faces south and we have the dream to convert it into a four seasons or sun room that can preheat or precondition the air for the rest of the building during the cooler months.
  8. PV array system with battery backup for electricity production, which should help with our zero energy goal and small carbon footprint.
  9. Wind turbine for electricity generation.
  10. Vegetable garden on the roof, which will help with the longevity of the envelope (in this case the roof), help with insulation (particular with the heat gain), and provide fuel for us, the inhabitants of the structure.

This sounds all very good, but we have to start separating the wheat from the chaff. Do these wish list items actually make sense? Do they fit our budget? Will they work together as a system and get us to zero energy, or will they be counterproductive? We have to find out through more research and the design process.

That vacant city lot – Part 2

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My first attempt to investigate the possibility of purchasing a vacant city lot alongside a listed property left the imprint of a brick wall on my forehead. Ouch!

Cathy and I thought about it and decided to try another angle. This time we focused on manager-level employees at the Department of Planning and Development (DPD). The bruises on my forehead must have shown and thankfully we were listened to this time.  We got a number of good follow up questions and were offered the opportunity to meet with a knowledgeable DPD team to discuss our plans. Not leaving anything to chance, we prepared and mailed a letter with all relevant information that same day.

I saw that brick wall approaching my forehead again at a frightening speed during the first ten minutes of the meeting, when the conversation seemed to flounder. Cathy must have been looking in a different direction: She steered the discussion with amazing confidence into “What purchasing options are out there?” and “What could we do that would make the dual purchase work?” Here is what we learned about the various purchasing options:

  1. Adjacent Neighbor’s Land Acquisition Program (ANLAP)
  2. Negotiated Sales Program
  3. Sealed Bid Program
  4. Neighborhood Group program (Through DPD)

The Neighborhood Group program appears the most viable option for our situation. It has the least risk of us ending up with the property but not the vacant lot. Cathy kept inquiring on how to initiate the acquisition process through the Neighborhood Group program.

We need an alderman’s backing, in form of a letter of support. All city property sales must go through the City Council, which makes the alderman support critical. Of course, sometimes plans for vacant city lots already exist (not all of which are immediately transparent) and so the lots are not available for purchase. To find out about any such plans we will need to talk to the DPD neighborhood project manager. This is another appointment to put on our list, right next to the meeting with the alderman.

That vacant city lot – Part 1

research, , , , ,

We have our eye on two properties, each of which has a vacant lot to the south. This combination of a property and adjacent vacant lot provides good solar access. The problem is that in either case we now need to buy two properties, not just one. Either property is only of value to us if bought in tandem with its adjacent vacant lot. It dawns on us that this has “complicated” written all over it…

We found out that both vacant lots are owned by the City of Chicago. This is good news! The city has built an impressive green agenda over the past few years and our pilot project should fit right into it. Time to call and investigate how such vacant lots could be acquired.

First lesson: don’t call with inquiries unless you have the Property Index Number (PIN) of the subject property handy. This is where the Cook County Assessor’s web page becomes handy. It has a search option where an address is matched to the corresponding PIN.

The phone call with the Department of Planning and Development (DPD) was curt and I was unable to communicate the sustainable scope and intent of our project. Before I could finish my introduction I was informed that if we could purchase the vacant city lot at all, it would take months – several months – like half a year… Trying to acquire the vacant lot in tandem with the adjacent building? Next to impossible.

I like the challenge of many problems and always have fun taking the extra effort and out-of-the-box approach while resolving them. Well, this phone call reminded me that not everybody shares this attitude or enthusiasm.