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Construction Math For Dummies

 
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Old 09-28-2019, 10:07 AM   #141
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Re: Construction Math For Dummies


The basic issues are getting moisture out of the structure (Showers, cooking, cleaning, etc.) and preventing condensation in the roof structure. I don't know your climate, but SLSTech has good info on his website, or you could PM.

Which opens up a discussion of HVAC and how airtight this will be....
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Old 09-28-2019, 10:13 AM   #142
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Re: Construction Math For Dummies


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Originally Posted by hdavis View Post
The basic issues are getting moisture out of the structure (Showers, cooking, cleaning, etc.) and preventing condensation in the roof structure. I don't know your climate, but SLSTech has good info on his website, or you could PM.

Which opens up a discussion of HVAC and how airtight this will be....


Exactly.

Time to get into this deep.

Been thinking about it.

2 fireplaces.
Range hood.
Pressure balancing....
EERV.....

Less concerned about internal moisture.

My main issue would be condensation.

SLS was exactly who I had in mind.
Buildingscience has some great stuff on the topic too.



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Old 09-28-2019, 10:25 AM   #143
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Re: Construction Math For Dummies


https://www.buildingscience.com/docu...r-all-climates


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Old 09-28-2019, 11:39 AM   #144
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Re: Construction Math For Dummies


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Originally Posted by BlueRidgeGreen View Post
Brings up another question.....

I had planned on spray foam for the entire roof profile.

Trying to save some money, and realizing I have plenty of space.....I am considering just a flash coat of spray foam and then like 16” of fiberglass.

What are my issues with a non-vented roof?
(Standing seam over full water and ice...)

Can I get away with only an inch or two of closed cell?


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I probably wouldn't. Could flash with 2" off CC and then build to R value with OC for 1/2 the price after that. Or vent it.
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Old 09-28-2019, 11:55 AM   #145
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Re: Construction Math For Dummies


Quote:
Originally Posted by BlueRidgeGreen View Post
Exactly.

Time to get into this deep.

Been thinking about it.

2 fireplaces.
Range hood.
Pressure balancing....
EERV.....

Less concerned about internal moisture.

My main issue would be condensation.

SLS was exactly who I had in mind.
Buildingscience has some great stuff on the topic too.



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You already know the ventilator takes care of the interior moisture, or is supposed to. I have experience with up here, Texas, but not Virginia, and none with ventilator based control.

I do know everything can be great, and if someone compulsively mops the floor there can be problems....
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Old 09-28-2019, 06:03 PM   #146
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Re: Construction Math For Dummies


Heat gain and loss wise you have ~475' of ~10' high walls, If built on a Square plan would yeild a 13,000 sq. ft. home....

I can't see just one ERV giving good service unless all the moisture sources are near each other.

This might be a good place for the use of whole room blown in expanding foam to seal missed holes/leaks in the air barrier, see JLC article.

Your Hvac person needs a sharp pencil, several mini-splits like an old ranch style motel? maybe a whole home forced air system for filtering and temperature leveling as the Sun beats down on thousands of sq. ft of walls?

Definitely use foil faced insulation on any sun exposed walls.

I hope there is a utility tunnel under the hallway for MEP . Hind sight is kicking in again...

No one worried about energy use or waste would ever build something of this shape where heating and cooling is required.... so expecting "normal" energy consumption is insane in my opinion, At some point the monthly savings won't ever cover the future value of the funds spent to lower it to a "normal" range for this size of home, Sq. Ft. wise.

You can teach a Bear to Dance, but it will never dance well.

It looks like a well built Bear though....
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Last edited by Fouthgeneration; 09-28-2019 at 06:14 PM.
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Old 09-28-2019, 07:18 PM   #147
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Re: Construction Math For Dummies


Quote:
Originally Posted by Fouthgeneration View Post
Heat gain and loss wise you have ~475' of ~10' high walls, If built on a Square plan would yeild a 13,000 sq. ft. home....

I can't see just one ERV giving good service unless all the moisture sources are near each other.

This might be a good place for the use of whole room blown in expanding foam to seal missed holes/leaks in the air barrier, see JLC article.

Your Hvac person needs a sharp pencil, several mini-splits like an old ranch style motel? maybe a whole home forced air system for filtering and temperature leveling as the Sun beats down on thousands of sq. ft of walls?

Definitely use foil faced insulation on any sun exposed walls.

I hope there is a utility tunnel under the hallway for MEP . Hind sight is kicking in again...

No one worried about energy use or waste would ever build something of this shape where heating and cooling is required.... so expecting "normal" energy consumption is insane in my opinion, At some point the monthly savings won't ever cover the future value of the funds spent to lower it to a "normal" range for this size of home, Sq. Ft. wise.

You can teach a Bear to Dance, but it will never dance well.

It looks like a well built Bear though....


I have a nice conditioned crawl for everything.

6’ section for the HVAC units....
Minimum of 3’6” throughout.
Opening up two (or more) hatches into the crawl at the central hall for ease of MEP rough in.

There was no HVAC engineering.
I have a guy who is exceptional, but I’m getting pushback from the Architect.

My guy wants one central multiple zoned forced air system and mini splits serving the furthest ends.

Budget....

Looks like this will be another corner cut.

(They throw money at the “art”, but want to economize on the practical stuff.
Driven by the (lead) Architect. )


Have I told you guys about the axonometric “sunshades” (that don’t really shade anything) that I’m trying to axe in favor of more efficient HVAC ?

It is what it is.

I had my HVAC guy meet with the client and I before the Archys arrived.

Best I can do.

If he wants to follow them down that path despite my objections.....
I keep cashing checks and nudging the ball in the right direction when I can.

I appreciate your thoughts man.
Keep em coming.


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Old 09-28-2019, 07:41 PM   #148
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Re: Construction Math For Dummies


Quote:
Originally Posted by BlueRidgeGreen View Post
Brings up another question.....

I had planned on spray foam for the entire roof profile.

Trying to save some money, and realizing I have plenty of space.....I am considering just a flash coat of spray foam and then like 16” of fiberglass.

What are my issues with a non-vented roof?
(Standing seam over full water and ice...)

Can I get away with only an inch or two of closed cell?


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Flash and batt works as long as it is thick enough to get the dew point in the foam layer. I’m not sure what zone you are in. Here in Massachusetts I did 3-4” of closed cell and the rest dense pack cellulose for my hot roof.

Last edited by Morning Wood; 09-28-2019 at 07:44 PM.
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Old 09-28-2019, 07:49 PM   #149
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Re: Construction Math For Dummies


Did you guys do any air sealing during the framing phase? Acoustical sealant, taping, gaskets etc? Do you have a goal ACH#? An ERV is a good way of idea if it is a fairly tight house. A fireplace in any kind of newer airtight building is just a bad idea in my opinion though.
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Old 09-28-2019, 08:40 PM   #150
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Re: Construction Math For Dummies


Quote:
Originally Posted by Morning Wood View Post
Did you guys do any air sealing during the framing phase? Acoustical sealant, taping, gaskets etc? Do you have a goal ACH#? An ERV is a good way of idea if it is a fairly tight house. A fireplace in any kind of newer airtight building is just a bad idea in my opinion though.
Fireplaces in old houses are a bad idea, nobody needs that loss of conditioned air 24/7/365.

Airtight stoves are pretty awesome.....
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Old 09-28-2019, 08:58 PM   #151
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Re: Construction Math For Dummies


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Airtight stoves are pretty awesome.....
And an oxymoron.

But yes, worlds better than a fireplace for more than one reason.

I abhor the thought of a house so tightly built that you need machinery to keep from suffocating. Sheesh.
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Old 09-28-2019, 09:00 PM   #152
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And an oxymoron.

But yes, worlds better than a fireplace for more than one reason.

I abhor the thought of a house so tightly built that you need machinery to keep from suffocating. Sheesh.
sorta like living in a refrigerator...
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Old 09-28-2019, 09:06 PM   #153
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Re: Construction Math For Dummies


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And an oxymoron.

But yes, worlds better than a fireplace for more than one reason.

I abhor the thought of a house so tightly built that you need machinery to keep from suffocating. Sheesh.
I have to remember to close my exterior doors with a lot less force if there’s a window open in my house. It’s almost like having one toilet in the house without a soft close seat and forgetting that it’s that one when you close it.
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Old 09-28-2019, 09:15 PM   #154
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Re: Construction Math For Dummies


Haven't built a fireplace on my own with out "outside" air feed pipe ever...

add a chimney pot top spring loaded damper to tighten up when cold...

and always install a Natural Gas(L.P.) pipe for a gas log/ starter. and you can use it to keep the house from frost damage when the power is out for a week or more.....

Where do you cook the neighbors post zombie apocalypse, if you don't have a working fireplace?

My eyes got tired walking the 125' hallway... did you lose any weight walking around the large footprint of home?

The introduction of chimneys into the peasant's huts and bungalows lengthened their dwellers lifetimes by keeping most of the smoke out their lungs and G.I. tracts, the downside being the home was now more vermin friendly and thatched roofs didn't last as many years with out the daily smoke treatments....
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Last edited by Fouthgeneration; 09-28-2019 at 09:20 PM.
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Old 09-29-2019, 08:27 AM   #155
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Re: Construction Math For Dummies


IMO any kind of wood burning device in a modern home should be positioned so it’s combustion air is outside the building envelope or at least not in conditioned space.
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Old 09-29-2019, 08:41 AM   #156
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Re: Construction Math For Dummies


Quote:
Originally Posted by BlueRidgeGreen View Post
Brings up another question.....

I had planned on spray foam for the entire roof profile.

Trying to save some money, and realizing I have plenty of space.....I am considering just a flash coat of spray foam and then like 16” of fiberglass.

What are my issues with a non-vented roof?
(Standing seam over full water and ice...)

Can I get away with only an inch or two of closed cell?


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Really depends on your climate zone. We have done 3" of closed cell to the roof deck before swicthing to fiberglass. Important that it is unfaced. You want the dew point to happen in the foam. Foam guy needs to know his stuff. Shouldn't build up a lot of thicknedd all at once.

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