1000sqft 2nd Story Apt Over Garage

slopecarver · 05-15-17, 11:37 AM

I'm just fishing for comments/suggestions/confirmation that my plan/system will work as I expect it to.

Zone 5 NWPA existing building is 42'Wx24'D with the long wall facing about 15 degrees off of south with nearly unobstructed southern view of the skies, West, East, and North walls are 90% shade and the building will be at the bottom of a 400' forested hillside to the north of the building ~4:12 slope (4ft rise for 12ft run) Open floorplan, 2-occupants, 1Br,1Bth

I'll be contracting a 2nd story addition to be built on-top of the existing structure with the same footprint, the existing roof will be demo'd. Construction will consist of open web floor trusses with 3/4" OSB T&G subfloor, 2x6 walls with OSB sheathing, energy-heel 4:12 roof trusses with a flat ceiling.

Insulation will consist of contractor installing 4" of XPS in 2" lifts on the walls exterior to the sheathing with staggered&taped seams, I will be installing by myself dense pack insulation in the 2x6 walls and under the floor with loose fill cellulose in the attic I may sub out this work however depending on cost. Attic insulation will be baffled near the eaves to retain free air-flow.

Insulation I calculate without factoring in sheathing or lumber to be R42 in the walls and I'm aiming for R30 under the floor and R60+ in the attic.

The air sealing plane I plan on being the subfloor, wall sheathing, and drywall ceiling. I don't know what to realistically aim for here but an ACH50 of 2.0 isn't unreasonable I feel.

Heating will consist of a single centrally located ASHP mini-split 100% inside the thermal envelope with mechanical ventilation. ERV? HRV? Ventillation returns to be in the bathroom (1) & kitchen (2), Supply in the bedroom closet (1) and living area (2).

Glazing will consist of about 64sqft of tilt and turn triple pane windows of various sizes. only 10% of the windows will be towards the north half of the building. Triple pane is specified because the building is about 250' away from a rural 4-lane highway with an unobstructed view that can be somewhat loud by experience. One 36" glazed man-door. All glazing will be flush with the siding.

Appliances: All electric, No exterior vents required. No Fireplace.

There are a few things I'm not sure about,

What model/size of HRV or ERV should I use? Supplier?
What model/size of Mini-Split should I go with? Supplier? I roughly calculate I need 30,000BTU of heat and a resistive baseboard heater backup would be a good idea. Design minimum temperature of -15F 98%, very rare that a night gets below that.

05-15-17, 11:37 AM	#1
slopecarver Lurking Renovator Join Date: Mar 2014 Location: Sugar Grove, PA Posts: 9 Thanks: 0 Thanked 1 Time in 1 Post	1000sqft 2nd Story Apt Over Garage I'm just fishing for comments/suggestions/confirmation that my plan/system will work as I expect it to. Zone 5 NWPA existing building is 42'Wx24'D with the long wall facing about 15 degrees off of south with nearly unobstructed southern view of the skies, West, East, and North walls are 90% shade and the building will be at the bottom of a 400' forested hillside to the north of the building ~4:12 slope (4ft rise for 12ft run) Open floorplan, 2-occupants, 1Br,1Bth I'll be contracting a 2nd story addition to be built on-top of the existing structure with the same footprint, the existing roof will be demo'd. Construction will consist of open web floor trusses with 3/4" OSB T&G subfloor, 2x6 walls with OSB sheathing, energy-heel 4:12 roof trusses with a flat ceiling. Insulation will consist of contractor installing 4" of XPS in 2" lifts on the walls exterior to the sheathing with staggered&taped seams, I will be installing by myself dense pack insulation in the 2x6 walls and under the floor with loose fill cellulose in the attic I may sub out this work however depending on cost. Attic insulation will be baffled near the eaves to retain free air-flow. Insulation I calculate without factoring in sheathing or lumber to be R42 in the walls and I'm aiming for R30 under the floor and R60+ in the attic. The air sealing plane I plan on being the subfloor, wall sheathing, and drywall ceiling. I don't know what to realistically aim for here but an ACH50 of 2.0 isn't unreasonable I feel. Heating will consist of a single centrally located ASHP mini-split 100% inside the thermal envelope with mechanical ventilation. ERV? HRV? Ventillation returns to be in the bathroom (1) & kitchen (2), Supply in the bedroom closet (1) and living area (2). Glazing will consist of about 64sqft of tilt and turn triple pane windows of various sizes. only 10% of the windows will be towards the north half of the building. Triple pane is specified because the building is about 250' away from a rural 4-lane highway with an unobstructed view that can be somewhat loud by experience. One 36" glazed man-door. All glazing will be flush with the siding. Appliances: All electric, No exterior vents required. No Fireplace. There are a few things I'm not sure about, What model/size of HRV or ERV should I use? Supplier? What model/size of Mini-Split should I go with? Supplier? I roughly calculate I need 30,000BTU of heat and a resistive baseboard heater backup would be a good idea. Design minimum temperature of -15F 98%, very rare that a night gets below that.