MossRoad
Super Moderator
- Joined
- Aug 31, 2001
- Messages
- 58,044
- Location
- South Bend, Indiana (near)
- Tractor
- Power Trac PT425 2001 Model Year
Exciting times for you! Good luck with the project and thanks for sharing the fun. :thumbsup:
Timber frame owner builder in NJ
- Thread starter emanaresi
- Start date
- Views: 11815
We will enclose with polyurethane sips. We also will be building a garage and a mudroom area connecting garage to house out of sips.
HVAC will be a geothermal open loop system. Our HVAC guy is very good but I think he doubts we will be as tight as we hope to be. He estimated equipment at about 6 tons, if I remember correctly, I think we will be able to downsize from that.
HVAC will be a geothermal open loop system. Our HVAC guy is very good but I think he doubts we will be as tight as we hope to be. He estimated equipment at about 6 tons, if I remember correctly, I think we will be able to downsize from that.
BitChin1
Silver Member
Be diligent here.
Ours originally spec'd 6T system along with the (2) 1T mini-splits we were adding in bonus room over garage and in loft area we did not want to run ducts to.
We finally agreed on a 3T system (pump-n-dump open loop). During recent cold spell we had no problem at all with most of the heating covered by the mini-split units (I think they would have been adequate by themselves but my wife wanted to keep door closed to bedroom areas and our basement was getting cool)
We did orient the house to take advantage of south sun exposure to high gain windows.
During last summer the mini-split from our loft provided most cooling (mid 90's)
I find that my Geo system does not operate very efficiently as it kicks on and off often unless we are at the extreme temps (hot/cold) and would have been ridiculous if we had gone with the 6T proposed.
My HVAC guy provided me the spreadsheets and SW he used to assess load - I made my own edits (vs the default values he uses) - then we "discussed" what system to install
We also used Poly SIPs for all except our small bump out for a pantry, the basement walkout walls and for our Bonus room over the garage - these areas were the primary locations we have air infiltration/thermal bridging (spray foam) - I think you will find the SIP rooms to be very well sealed (provided your installer pays attention to seams and plates - use EDPM gaskets as much as possible.
Our next biggest "leak" was our HRV - I have since sealed this unit and am not using it - in KS we get enough breaks in the weather that windows are opened and general traffic through doors, dryer etc provide air exchange. Have run into some excess humidity at sub-zero temps and we used bathroom exhaust to alleviate this.
Thanks, yes, I am doubtful that we will need the system to be as large as specified. I have agreed with the hvac installer to reevaluate before we install any equipment but after the sips have been installed. We will be either spray foaming or putting rigid foam on the basement walls, and I plan to condition the basement though it will not be finished until a later date. Total sq footage including the basement is about 5500 sq ft and there are quite a few cathedral areas. He provided me with the calcs that he did in order to apply for permits but I think there is room to make changes to further capture the airtightness and insulation value of the house. I do plan to use epdm gaskets on the sills and other areas that could become air infiltration ares.
I am surprised you decided to eliminate you hrv...it seems they are very strongly recomended due to tightness of the house. We do plan to have windows open during the more mid months, but probably 6 months of the year the house will be sealed up. We plan to install an ERV.
How big is your house? what did you do for windows and doors? CAn you provide me with your calcs? or maybe tell me what were the assumptions that were most "wrong" in your hvac contractor's calculations?
I am surprised you decided to eliminate you hrv...it seems they are very strongly recomended due to tightness of the house. We do plan to have windows open during the more mid months, but probably 6 months of the year the house will be sealed up. We plan to install an ERV.
How big is your house? what did you do for windows and doors? CAn you provide me with your calcs? or maybe tell me what were the assumptions that were most "wrong" in your hvac contractor's calculations?
I forgot to say, the frame is eastern white pine, hand selected trees by our timber framer in Maine. He fell them, and sent them to his sawyer. It's been a fun process so far and we are just getting started.
The 3rd level "lofts" will just be a type of attic, we will probably use ships ladder style things to get up there. The one over our young daughter bedrooms we believe will be a nice pseudo private living area for them. A place to play fort when they are young and maybe a quiet reading area when they are a little older. Or maybe they'll have no interest in it and we'll have to find some other interesting use for it.
The 3rd level "lofts" will just be a type of attic, we will probably use ships ladder style things to get up there. The one over our young daughter bedrooms we believe will be a nice pseudo private living area for them. A place to play fort when they are young and maybe a quiet reading area when they are a little older. Or maybe they'll have no interest in it and we'll have to find some other interesting use for it.
tkappeler
Platinum Member
What is the R value of the SIPS? We are NJ also, same climate zone. We used Raycore's (closed cell poly with studs cast in them, foil vapor inside and out) 2x4 walls which are R26 and R45 for the ceilings. I was not sure how well it would work but it has exceeded my wildest dreams. Even on the coldest days a week ago (polar vortex
), it took over 6 hours for the temp inside to drop down 6 degrees. Our heater only runs 203 times per day with the high efficiency fireplace handling 1/2 of the house.Looking forward to your updates.
The walls are 4.5" R28 roof 6.5" R40. I did read most of your thread. I'm glad the performance has been pleasing. I expect we will pay some performance price since we are building a masonry fireplace. Not a high efficiency, but we will pay the price to have the fire we want...
BitChin1
Silver Member
As for the HRV/ERV - I would suggest you include it (in my case it was ~ $600, so best to have it and not use vs need it and not have it:thumbsup
In my case I just found that it along with my bath fans and typical 30mph+ wind I was getting a wind tunnel effect between the HRV intake and my bath exhaust - after closing off the intake this has stopped and I am not noticing any ill affects of not running it - other than high humidity and your ERV won't reduce humidity much - the frame, along with other building materials hold quite a bit of moisture along with tight walls it does not escape from showers, cooking etcMy house is 1925sqft on main level, 2200sqft in basement, 500sqft bonus room (13,500ft^3 within the insulated boundary). main level great room is a large vault 29' to the peak(3 Bent at 1150sqft ~ 550sqft of which is a loft) - so slightly smaller than yours. also mine is a bit more "cubic" (less surface area) - my total volume was ~ 64,500ft^3 (I don't recall my surface area)
I will see if I can find the files we used for final calc (it was on his computer but I think he printed me a copy)
For windows I used Crestline from Menard's - inexpensive, but seem to work well. Main reason (other then cost) was they allowed me to special order my glazing for no extra cost!
I have 35 windows about half operable other half fixed. my glazing for most windows is their triple pane Zo-e-shield 8 low heat gain (standard in my area)
for 2 large main level picture frame (facing South) I used the double pane Zo-e-shield (could not provide 3 pane in this size) and for 4 large windows at 2nd level (above 10 tie beam) I used a special order Cardinal Glass 180 (I think it was) high solar gain
Doors I used Menards Mastercraft (planned to replace some time in the future but they were inexpensive and did not worry about damage during construction - so far they work well and look nice
Primary issue in the HVAC calcs was air infiltration rates - default was 7ACh! we did early test at 1.1ACh (blower door) w/o window/door insulation nor adjusting windows doors etc. Bonus room, pantry and basement did not yet have spray foam - so just the OSB and exterior WRB (sprayed/brushed Tremco - I really liked this product) providing air sealing.
They also assumed worst case air temp but that rarely occurs and then not for long periods.
Heat load they used default code minimum for window glazing and provide no credit for solar gain during heat calcs (my windows provide 80% of heat load over typical heating season) - we added a TF eyebrow to shade the high gain windows in summer
the other issue was that his load calc suggested we needed just under 5T, HVAC proposed 6T - "just to be safe"
problem is this is safe from a "don't call me back" but it leads to inefficient operation.My calculation showed I needed 2.25T but the 3T was smallest unit - I could have got by just with adding another mini-split in the basement and been fine
(but with 30% tax credit on the Geo system (all costs involved) I netted ~ $9k for the system cost of the geo (I used well to well open loop so not cost for tubing field or deep well etc)
to help with passive solar I used 1" concrete based with 3/4" stone for main floor - tiled our basement floor (with 2" R10 foam under slab) -
my SIPs ar R24 wall, R40 roof - basement is 2x8 stud with 2" closed cell, 5" open cell (so ~ R21 full wall) Bonus room was 3" closed cell with 9" open cell above 10', and 3" closed cell/R30 fiberglass batt elsewhere (foam guy ran out and I did not want to wait 3 days to close up ceiling)
I'm surprised your doing an open hearth. Doesn't an open hearth pull warm air out of the living space for combustion?
