Starting an HVAC Project on my Own...

Discussion in 'HVAC Heating & Cooling' started by moparfreak, Feb 18, 2014.

  1. moparfreak

    moparfreak New Member

    Messages:
    11
    Location:
    Wisconsin
    Hello folks,

    First time here, got the link over from Garage Journal. Looks like a great wealth of knowledge here! Anyways, I am embarking on a large addition to my ranch house right now, expanding the garage and kitchen, and adding a half bath on that end, and redoing the laundry room. To give some reference here's the plan:

    Remodel Plan.jpg

    Aside from the foundation, framing & electric, I am doing the entire remodel/addition. I am generally very handy, and have most tools needed, etc. But, most of my experience lies with replacement and repair, not starting from scratch.

    So with the HVAC aspect of this job, I'm at a loss with what's the best way to approach this? How do you plan out the extra heat runs? There is an existing branch used for kitchen and laundry room. I am assuming I can just extend or repurpose that branch for the kitchen/bath/mudroom vents that are needed. There is also a shop furnace I'll be hanging in the garage (Mr. Heater or similar) that I plan to feed off the existing flexible dryer NG line. Are these assumptions on track? I don't have experience to know otherwise and certainly don't have any friends or colleagues who've done this.

    I have a little bit of time with the weather here in WI preventing much progress on the foundation and framing, so I'd like to make sure I plan this right so when I start, but what is the best way to go about laying out the HVAC infrastructure? Are there any good resources I can follow? I do have the code available and a helpful inspector so I will be reviewing that closely and getting his signoff before starting. Do HVACers typically make up a schematic that has to be reviewed?

    Just not sure how to go about this and get it started. Any advice is much appreciated!

    Thanks,
    Adam
  2. DonL

    DonL Banned

    Messages:
    4,005
    Location:
    Houston, TX

    Welcome to Terry's Forum.

    Most HVAC installers will need a license to install, especially when refrigerant it used.

    A good place to learn would be a website that teaches you how to pass the test to be a HVAC installer.

    You could also get a required State License out of it.


    Good Luck.
    Last edited: Feb 18, 2014
  3. Dana

    Dana In the trades

    Messages:
    2,812
    Location:
    01609
    Optimal heating solutions usually start with a room-by-room heat load analysis, and in your case, both the before & after versions of the rooms under revision/expansion. Either a Manual-J or I=B=R approach would work, but use realistic 99% outdoor design temps, not the absolute seasonal low, and reasonable indoor design temps (68-72F, not 78F or 60F)- no thumbs on the scale or you can render the result meaningless.

    You have a great deal of control over the "after" picture of the heat load during the design phase of the house. But if a lot of exterior roof/wall/window area is being added it may require going a bit beyond code-min to be able to simply extend the heating runs that currently serve that end of the house. But building to better than code is not a disaster- a code-min wall is just the crummiest wall assembly that you're legally allowed to build. Going better than code on R values & U factors has a nice comfort uptick at the outdoor temperature extremes (not that it ever gets COLD in Wisconsin, eh? ;-) )

    Sometimes building a tighter better-performance addition will even LOWER the overall heat load, particularly if you're starting out with 2x4/R13 construction (about R10 after thermal bridging) and bumping up 2x6 blown-insulation with 2" of exterior foam under the siding (about R22-24 after thermal bridging), and old clear-glass double-panes that run U0.6 ish being replaced by more window area, but using U0.25-U0.28 windows. The heat loss out of the better than code wall is less than half that of the 2x4 wall per square foot, and the better than code windows lose less than half the heat of the old clear double panes, so quite a bit of exterior surface can be added without increasing the heat loads.

    Getting a reasonably high R on the sloped ceiling dinette section can be tricky, but if you don't it's easy to end up with ice-damming & water incursions in winter. Without the full 3-D view it's a little hard to guess what's going on there and how it might be best addressed. In general cathedaral ceilings work better as unvented assemblies, with thick rigid foam on the exterior, at least to the IRC prescriptive min for your climate zone (which is either zone 6 or 7 depending on where you're located in WI), and blowing the rafter bays full of cellulose, with no interior side vapor barrier.
  4. DonL

    DonL Banned

    Messages:
    4,005
    Location:
    Houston, TX
    You should buy Dana's book.

    It has some great info in it.
  5. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,137
    Location:
    Maine
    Repurpose what branch? Hot water, steam, forced warm air? This is a joke right? You have no experience or skills related to HVAC and you really think you can handle that?
  6. moparfreak

    moparfreak New Member

    Messages:
    11
    Location:
    Wisconsin
    Dana,

    Thanks for your reply. A lot of great information that is really helpful. Yes, as you suspect this is an older house with 2x4 construction and leaky double pane windows, so although I'm adding some more surface area and windows with the addition I expect to make improvements. This winter has been especially bitter with a number of days sub negative teens, so although I'm in SE Wisconsin it's been rough.

    Here's the roof plan, you picked up on the vaulted ceiling.

    Roof Plan.jpg

    My plan was to go with R-38 batting in the vaulted ceiling with baffles to vent to the ridge. I wasn't aware that in cold climates, hard foam and unvented ceilings were common practice. I'll talk to my builder about that.

    The mud room / bathroom is going to essentially use the existing heat runs (forced warm air) that were already present there (pre-demo there was a laundry room and office there), so the only added living space is the dinette itself. Since I've actually reduced the sq. footage of the house (weird, I know...) the inspector didn't feel the need for heat loss calcs but I will definitely proceed with this to make sure I've targeted the correct R-values where needed.

    If you do have a book that covers this type of thing I'd definitely be interested, where would I look to for this?

    Thanks,
    Adam
  7. Dana

    Dana In the trades

    Messages:
    2,812
    Location:
    01609
    High density R38 "cathedral ceiling" batts with an inch of ventilation gap might meet code-min (but also might not- haven't looked in detail at WI code), but it's not enough to prevent ice dams, and if doesn't have sufficient pitch (6:12 minimum) even with soffit-to-ridge venting it might not be enough to fully protect the roof deck from moisture damage.

    If you stick with the R38/vented approach your best bet would be to use a poly vapor barrier under the ceiling gypsum caulked at the edges with acoustic sealant, and don't put ANY holes in the ceiling gypsum for lights, fans etc. Sealing of the vapor barrier at the ridge beam is super-critical, since air leaks at that location are all but guaranteed to have mold or rot issues at the peak of the roof at some point if you don't.

    The skylights are also going to present a real ice-dam genration issue in your climate, especially if they are a type that can be opened. Sure you really need them? Clerestory windows on the end wall are a safer bet for daylighting. There are some ridiculously expensive triple-pane skylights from Europe as well as some even MORE ridiculous aerogel (hazy, not clear) skylight options out there, but even those would have issues when the snowpack exceeds a foot or so. (I have nearly 2' of snow on my roof right now, and two double-pane Velux skylights- trust me on this one!)

    Another approach that won't meet the letter of code but still works is to use 2" of closed cell foam sprayed onto the under side of the roof deck, and fill in the rest with dense packed cellulose (3.5lbs per cubic foot nominal) or dense-packed new-school fiberglass (1.8lbs minimum) such as Spider/Optima/L77, and no interior side vapor barrier, just air-tight gypsum and standard latex paint. This is outside the bounds of IRC recommendations, but has been intensively studied by building science types both in the US and Canada- it works. With dark asphalt shingle roofing it works even with 1" of closed cell foam- see the rows for International Falls and Minneapolis in Table 3 of that document. SE WI is the warm edge of US climate zone 6, so it it works in zone 7 (Int'l Falls), it surely works in your neighborhood.)

    [​IMG]

    In any new construction in climate zone 6 it's almost a crime to build an exterior wall with a "whole wall-R " of less than R20 (and that's what would become code-min if/when WI adopts IRC 2012). That would have half the heat loss per square foot of the 2x4 construction it replaces, so you probably wouldn't need to add air-flow to heat the additional space. An example of an R20 wall would be 2x6 16" o.c. with R21HD fiberglass or R23 rock wool batts plus R5 of insulating sheathing. But a better R20 wall would be 2x4 16" o.c. w/ R15 rock wool and 2" of exterior EPS, since that keeps the structural wood warmer and drier, and you can then skip the interior vapor retarder, giving the wall assembly much greater drying capacity. It's even about an inch thinner than a 2x6/R20 + R5 solution. To have something to hang the siding on it's customary to hang 1x4 furring over the foam through screwed to the studs 24" o.c. and use shorter ring-shank nails or screws to hang the siding.

    Air sealing is essential- a bead of acoustic sealant type caulk between every framing element and the sheathing goes a long way, as well as foam-sealing any electrical & plumbing penetrations of studs, plates or sheathing. Don't forget to air-seal between doubled up top plates, and between the bottom plate and the sub-floor, etc.
  8. houptee

    houptee Member

    Messages:
    182
    Location:
    Monmouth County, NJ
    There is an article in this month Journal of Light Construction all about insulating cathedral ceilings.
    You have to be a subscriber to read it tho or go to the local library and see if they have the magazine subscription.
    Our county library has a lot of magazines and code books but you cant check them out.

    http://www.jlconline.com/ceilings/insulating-cathedral-ceilings_o_2.aspx
  9. liamhvister

    liamhvister New Member

    Messages:
    4
    Location:
    oklahoma
    I think it wouldn't be that easy without proper training.
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