Davenport House Restoration Update - Green Architecture

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Davenport House Restoration Update - Green Architecture

Post by pharding »

Heating, Ventilating and Air Conditioning System is currently approximately 75% installed. Last year the HVAC system was designed by a fine engineering firm to the Green Architecture criteria that I established. There was a modest premium for the system which had to meet the following criteria:

1. Fit into the historic fabric of the house and its extraordinarily tight space constraints. Grilles and diffusers were to be invisible or very lowly visible.

2. Ultra high energy efficiency within or close to a moderate budget.

3. Ultra quiet forced air system. No vibration noise.

4. Ultra clean and comfortable air.

5. Absolutely no visibility of HVAC equipment on exterior walls, roof, and ground plane around the house.

6. Absolutely no space pack HVAC system because of its poor performance quality.

The system serving the second floor includes an HVAC unit in what was originally the second floor attic. The house has a low attic height due to FLW's clever manipulation of the building volume to reduce the original construction cost. The central chimney limited the available space even further. I used the highest efficiency HVAC equipment available which meant that the furnace burns very hot. This triggered a need to enclose the HVAC unit in a fire rated mechanical room. We insulated the space between the rafters in this room with ultra high performance polyisocyanurate board insulation and left a 1" space beneath the wood deck for ventillation to avoid dry rot of the wood structure. We attached 5/8" gypsum drywall to the underside of the wood rafters. We replaced the ceiling joists with deeper members in this area to fix sagging ceilings and to provide a structurally adequate, vibration free floor for the mechanical equipment. We built insulated 2 x 4 walls around the mechanical room. The walls had drywall on both sides with caulked joints to contain the noise within mechanical unit and to keep the equipment noise out of the master bedroom. The unit selected, in addition to being very high efficiency, had a variable speed fan motor. The variable speed motor is critical for increased energy efficiency and for quiet heating operation. We used the highest efficiency condenser which was both energy efficient and allowed the fan motor to operate at two speeds when air conditioning.

In addition to unit selection other strategies were employed for ultra quiet HVAC operation. The unit itself rested on isolation pads to control unit vibration which generates noise. Typically residential HVAC systems are contractor designed. By having an engineer design the system, including the ductwork, we were able to improve the overall quality of the system by specifying larger ductwork. Larger, lined ductwork reduced the air velocity for the HVAC system. The result is lower air velocity which is both more comfortable and quieter. The mechanical contractor, who is doing a great job in general, unfortunately did not think that I was serious about the specified duct sizes and fabricated the ductwork smaller with 1/2" insulating liner instead of the 1" indicated on the drawings. He also fabricated the ductwork without getting our approval of the shop drawings. After a candid discussion the incorrect ductwork went to the scrap heap and I agreed to do the shop drawings with his input. This also included the usual impolite conversation. We had to then cycle through a series of meeting with the heating contractor to figure out how to get the larger than normal ductwork through incredibly tight attic spaces. Once this was resolved, we had to wait for an opening in his schedule to get the work done. Currently the ductwork is fabricated and 50% installed in the attic. The grilles had to be in the ceiling. We needed the most minimal look possible. We used 1" linear diffusers without a frame on the ceiling. The supply grilles are on the outside wall centered on windows. When one looks into the room the supply opening is so subtle so as to be invisible to the casual observer. Each room has a 1" wide return grille located above the door opening so as to hide it as much as possible.

Air quality was significantly improved with the highest quality electrostatic air cleaner available and the enhanced furnace filters. The insulating of the attic mechanical room allowed putting a humidifier on the system.

On the second floor existing 1901 floor grilles were left and blanked off to maintain fidelity to the original fabric of the house. On the first floor existing floor grilles were reused. Where additional grilles were required, we purchased more 1901 floor grilles from a Chicago building salvage company.

The system for the house had two units which effectively zoned the house for increased comfort and energy efficiency. The attic unit served the second floor. The basement unit served the first floor and the basement. For the sake of fidelity to the original basement design, I did not want ceiling drops or soffits to hide the ductwork. Ductwork is stacked vertically along on outside wall and it runs between the joists.

I did not want our restored FLW house to have modern mechanical equipment visible on the exterior. The high efficiency equipment requires both combustion air and exhaust. Rather than pipes sticking out of exterior walls and the roof of the house, we used abandoned flues in the chimney. The condensers with their cut-off switches are typically pad mounted outside of the house. We took this equipment and buried in a new concrete areaway adjacent to the house with a steel grate on top of it.

Building Insulation

We wanted the exterior envelope to highly insulated and yet allow the house to breathe. The goal was maximum energy efficiency, very air quality, and avoid problems associated with toxic mold in the exterior walls. We will fix an awful decision made by the previous owner. The cypress exterior siding was painted approximately 5 years ago. This trapped moisture within the exterior walls and caused fairly rapid deterioration of the exterior cypress siding. This summer the siding will be stripped and refinished with stain to match the original FLW design. This will allow the exterior walls to breathe. Consistent the desire for the outside walls to breathe to extend the life of the cypress siding and to avoid mold within the walls, we took an innovative approach to insulating the house. We used insulation that designed for use in the humid south to address this problem. We used mold resistant batt insulation. The insulation is formaldrahyde free so that it would off gas harmful fumes into the house. It also has a special mold resistant paper face. We did use the typical PVC face because in our opinion it traps moisture within the house. We wanted the exterior walls to breathe. The batt insulation also had higher than normal r-values per inch of thickness. In areas where the ceiling was attached directly to the underside of roof rafters we used polyisocyanurate insulation with taped joints to maximize energy efficiency within a 4" space and allow 1" for ventillation of the roof assembly.

The restoration of the Davenport House is being done with maximum fidelity to the original FLW design and "Green Architecture" strategies. The result is that for a very modest increase in cost the house will be extremely energy efficient with a very quiet HVAC system, and extremely high indoor air quality. The house will dramatically reduce its need for fossil fuels and help to preserve our fragile and precious planet.

Copyright 2006 Paul Harding
Paul Harding FAIA Restoration Architect for FLW's 1901 E. Arthur Davenport House, 1941 Lloyd Lewis House, 1952 Glore House | www.harding.com | LinkedIn

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Re: Davenport House Restoration Update - Green Architecture

Post by DavidC »

pharding wrote:Copyright 2006 Paul Harding

Huh - ???


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