Heat loss calculation and sizing radiant runs

Mcg01

Hi first post here. I like to star by saying thanks for all the information I've learned from This site over the years. 

 So I'm remodeling my kitchen and dining room and will be putting hydronic radiant heat in the floor.. (knocking down a wall so it will be one room about 11×22)
 I would appreciate some help with the sizing and any other advice anyone could give. 
This is what I have planned so far.
I have a heat loss calculation for all the rooms in my house attached 
The floor is going to be original 1x8 tongue and groove sub floor. With a mud job and ceramic tiles over the mud. 
 The heater is a 6 year old triangle tube solo 60 that I installed myself. 
I plan on making a 2nd zone for the kitchen/dining  radiant. 
 I understand how important it is to size these systems properly.
 Would someone be able to look at my heat loss calculation and lead me in the right direction. 
 Also if there are any text books you could recommend I would love to read up on this but I'm not sure where to start.
 Thanks in advance 

jesmed1

Not a pro, but a mechanical engineer homeowner who has done heat loss calculations using a variety of methods. First thing I would ask is where you're located, as your design temp affects your heat loss. It looks like you're using a design temp of 17 degrees and a delta T of 53, which means you're not in the far northern states.

Second thing I would ask is when your house was built, and type of windows and insulation. Below is a good general guide to the range of heat loads you can expect for various house vintages and windows/insulation.

https://inspectusa.com/blog/typical-heating-cooling-loads-in-older-homes/

Your house total comes in at 31.6 BTU/sq ft, which falls into the "Type B" house above. Check the characteristics of a Type B house and see if yours does fall into that category.

But beware of making assumptions based on house vintage. Our 100-yr-old 4-unit condo building in the Boston area (colder than your area) has a heat load of just 20 BTU/sq ft, which makes it as good as a Type A "recent construction" house. So be careful about assuming what range you should be in based on age.

If you have heating bills from last season, this is a very accurate way to calculate your heat loss based on your known BTU consumption during a cold month, and known weather data (heating degree days) from that same period.

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

Once you get some confidence that your overall heat loss numbers are accurate for your house type and area, then you can have more confidence that your room-by-room numbers are correct.

Mcg01

Thanks for the quick reply jesmed1. I live in NYC suburb. My house is a completely detached Dutch colonial built in the late 1920's
 I gut the top floor 5 years ago and used 3" of closed cell spray foaming the walls and 8" of rockwool in the top floor ceiling joists. 5/8 sheetrock
The windows were replaced with contractor grade vinyl windows with argon..
 I don't think my heating bill will help with assessing my heat loss because the house is still very leaky. Which is one of the reasons I'm doing the first floor this year  And sealing the sill plates in the basement.
I'm also going to be re doing the siding. Complete tear off. I'm going to use house wrap and exterior insulation with CertainTeed cedar impressions siding on top. And will fill the roof rafters with closed foam whe. I replace the roof. (Probably within a year or 2)
So hopefully  the house will be much tighter after I do the 1st floor. And even tighter when I do the siding and roof.
I am aware of the need for makeup air. I will do a blower door test when the time comes.
 The heat loss calculation that I attached in my last post was done by a very knowledgeable guy from my local plumbing supplier.  He did the calculation using the future alterations in mind. I tried to reach out to him but He's retired

 As far as the heating goes the kitchen/dining/ small bath will be radiant and the rest of the house will be cast iron baseboard.
I'm flirting with the idea of running some radiant loops in my 1st floor floor joists under the living room and sun room hard wood floors to use floor warmer not necessarily as a heater. 
 Thank you for the links to the articles I will give them a read and see if I can fine tune my numbers.  

 I know it's hard because I'm doing the house in stages but would you be able to give me an idea on how to go about designing the radiant? It seems like every contractor I talk to just does it by the square footage of the room. I'd rather not do it that way but it is such common practice around here it makes me wonder if I'm over complicating things or of everyone else just wants to make a quick buck and not concerned with making the house run efficiently.
 Thank you again 

hot_rod

Tube above or below the floor?

EdTheHeaterMan

How thick is the mud base for the tile floor? If you can make it at least 1" then stapling 3/8" tube to the top of the 1x 8 T&G will give you a better job. 1-1/4 mid base would be better.
That way you can use 6" tube spacing near the outside wall(s) then move to 8" or 10" spacing closer the the center of the home.

If you are going to staple up to the bottom of the sub floor, then you are stuck with 8" spacing if you have 16" on center floor joist. And there is lots of drilling and threading tubing thru the holes between the floor joist. (this is the reason @hot_rod asked above or below?)

jesmed1

Mcg01 said:

Thanks for the quick reply jesmed1. I live in NYC suburb. My house is a completely detached Dutch colonial built in the late 1920's
 I gut the top floor 5 years ago and used 3" of closed cell spray foaming the walls and 8" of rockwool in the top floor ceiling joists. 5/8 sheetrock

It sounds like when you're done, you'll probably have a heat load of 20 BTU/sq ft or less overall. Meanwhile, the roughly 30 BTU/sq ft your contractor came up with is probably reasonable for now. As you know, air infiltration can make a big difference, so your blower door test sometime in future will tell you much.

@EdTheHeaterMan and others here will give you good guidance on the radiant design.

Mcg01

Thanks. In the mud job in the kitchen and bathroom. I can probably do 1 1/4 mud. 
 Should I limit the length of the run to 250' for the 3/8 per?
 Also the length is total length from the manifold right?
 Should I try to keep every loop the same length. 
 Forgive me for all the noob questions. It's my first radiant job and I'm having trouble finding literature on how to do it. .

hot_rod

I'm a big proponent of 6" on center spacing. You get better output, faster recovery, and more even temperature across the floor surface.

6" can be done with 1/2" pex. 3/8" is easier to work with, certainly for DIYers. . I'd go 200- 225' with 3/8"
You can get either in a 1-1/4" mudset. Staple the loop ends well, that is where it tends to want to pop up.

Are your floor joist up to the task of that extra weight? Nothing worse for tile than a bouncy floor

EdTheHeaterMan

Mcg01 said:

Thanks. In the mud job in the kitchen and bathroom. I can probably do 1 1/4 mud. 
 Should I limit the length of the run to 250' for the 3/8 per?

200 max on 3/8"

Also the length is total length from the manifold right?

YES, We try to place the manifold close to the center of the job so the run out and back will be counted as actual heating ares and try to stay away from long runs to get to the heated area.

Should I try to keep every loop the same length.

Yup within 20 ft either way.

Forgive me for all the noob questions. It's my first radiant job and I'm having trouble finding literature on how to do it.

Forgiveness is assumed here. We all needed to learn this stuff at one time or another. Sometimes by trial and error ...and you can benefit from our errors so you ' make them. We like to share the knowledge here.

EDIT:
Where are you getting the tubing? Make sure it is oxygen barrier to offer you more flexibility in what pumps and boilers you can attach to the system. Sometimes the tubing manufacturer will do the load calculation for you. At least Wirsbo did have that service 20 years ago when I was designing systems for my customers. They would even send out CAD drawings of the tubing placement and design

Mcg01

Great thanks  so much. I'm going to do more planning and I'm sure I'll be back with more questions. I'll try to draw out my loop designs and make a parts list to post it up here for you guys to review.. stay tuned 😉 

hot_rod

A 3/8" loop with a .3 gpm flow would be 3.5'head. A 250' loop is 4' head, so not a huge difference, as far as pumping.

If you buy a coil that is 500', use 250' loops. If you buy a 400' coil, use 200' loops:)

+ or - 10% on loop lengths.

Mcg01

What changes when designing a radiant floor by using square footage alone vs using a heat loss calculation? 

mattmia2

The heat loss tells you how much heat it has to output which tells you how much tubing you need so it dictates your loop spacing. It may tell you that you need some supplemental heating like a pane radiator to get adequate heat.

Mcg01

Just saw your edit Ed the heat man. I'll reach out to my local plumbing supplier and see what they can do. 

Mcg01

Hot_rod. Thanks for the picture what's that card called I want one lol

EdTheHeaterMan

First thing is... you will know if the floor has enough BTU capacity to heat the space at a reasonable temperature. My home in Brigantine NJ for example has an addition with vaulted ceilings that will heat all the way down to -5°F outside temperature.(Well insulated). But the rest of floor heat in the home, built in the 1970s, will only heat the home above 16°F outdoor temperature. When it gets colder than that, I need to turn on the old gas furnace and blow some warm air thru the ductwork.

The BTU per sq ft of the floor area may not change, but the amount of heat needed will increase as the outdoor temperature decreases.

Does that answer your query?

Mcg01

Yes Ed thank you much clearer to me now

Mcg01

Thanks mattmia2

hot_rod

Mcg01 said:

Hot_rod. Thanks for the picture what's that card called I want one lol

RadPad is a slide rule calculator that Larry Drake developed. I think he has an online version now. Very handy for quick calcs. It lets you play with spacing, lengths, flow rates, floor temperature BTU output, etc.
You do need that room heat load first.

https://drakeip.com/RadPad/RadPadFiles/RadPadSideB.html

Mcg01

I messed around with that rad pad slide rule today. Thanks again. I'm leaning a lot. 
These were my findings. I think I'm going to need at least 2 zones. 

Mcg01

I also found this manual from upanor I'm going to thumb through it tonight while working thebnight shift. https://www.uponor.com/en-us/customer-support/order-manuals#radiant-heating

Mcg01

I also sent a request for a quote to an online supplier that says they do the heat loss calculation for me and tells me everything I'm going to need. 
The information they asked for was very limited. I gave them as much information as I could. I'm curious to see what they recommend