Radiant Slab on Grade Heating Source Choise
Last Post 08 Jul 2022 01:48 PM by sailawayrb. 9 Replies.
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Thomps0990User is Offline
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05 Jul 2022 06:31 PM
Hi all, I've come for some help form the pro's I'm Building a new home in Ontario, Canada. 1750 sq ft Slab on grade. Have heat loss calcs and Have had a 30k BTU boiler spec'd My original choice was to use propane, mains gas not avaliable in my area. Now I'm wondering if my slab will be enough of a thermal battery to sustain heat throughout the day and use an electric boiler to heat through the night during offpeak energy usage. My question is where does the $/KWH need to be to be the same as LPG @ 75 Cents/L Current price. Im having a hard time trying to figure out where these two energy prices and measurements equal out.
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06 Jul 2022 10:49 AM
You need mass to carry you through the night. ICF will working the spring summer and fall but not in the dead of winter. I am in lower Michigan and I can get away with 4 months of no Heating or AC but in summer we run it maybe 20 days now....I have automated an attic fan to monitor if a window at one end of the house is open and if it is and the temp outside is under 60F and House is above 67F then it turns the attic fan on.

I would do a air source heat pump/Mini Split with small supplemental propane heater. That way most of the time you are super efficient and have AC for summer and then on the -10 degree days use propane as needed. An electric boiler will be expensive to run and install. We have natural gas but use a regular 40 gallon NG water heater to completely heat the floors in a 7000 sqft house and also heat the water with no problem. I would just use a domestic hot water tank, much cheaper.

"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
sailawayrbUser is Offline
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06 Jul 2022 02:45 PM
Let's see:

$0.75/L
25,000 Btu/L
3,412 Btu/KWH
0.75 X 3,412 / 25,000 = $0.102/KWH

But an electric boiler is 100% efficient and a gas boiler is maybe 90% efficient. So the breakeven point would be an electric rate of about $0.114/KWH.

You can get an electric NextGen boiler for about $1,200 USD. This boiler eliminates the need for an expensive hydronic radiant panel (e.g., air separator, controller expansion tank, differential pressure valve, pumps, relief pressure valve, etc). In addition to being legal and rated for space heating unlike a hot water tank, this boiler cycles the pumps during the non-heating season to keep them from seizing up and also avoids the parasitic heat loss of a hot water heater. The NextGen boiler also has off-peak capability and outdoor temp reset to deal with rapidly changing outdoor temp.

https://www.borstengineeringconstruction.com/NextGen_Boiler.pdf
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
Thomps0990User is Offline
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06 Jul 2022 02:59 PM
Thank you very much for this math. I've have been looking at the NextGen Electric boiler and it is very appealing. My troubles were determining the breakeven point compared to propane @ the current price. Considering my Offpeak price is $0.85/kWh Mid Peak is $0.119/kWh on peak is $0.176/kWh The ontario energy board is also working to implement an Overnight rate of $0.022/kWh IF that were to happen I feel the overnight rate would be the majority of the load demand for the boiler Its seems anything other than on peak would be about a break even Minus the associated delivery fees with both fuels. My other issue now becomes what size of whole home generator would I need to provided backup power to keep this boiler running during a power outage. Any idea where I could find a dealer in Ontario that sells and services the NextGen boiler? Also I believe I would need the 12KW version.
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07 Jul 2022 02:09 AM
Just contact todds at symbol nextgenboiler dot com. Please tell Todd Seed that we referred you...one of our affiliates...and he should be able to help you well. I wouldn't recommend going any bigger than your 99% 30k Btu spec...as long as your heat loss analysis was done properly. The NextGen boiler power requirements may be found in the Installation Manual available in one of the links you can find via the previous link I provided. By the way, the internals of NextGen boilers are easily DIY replaceable and serviced, .e.g., unlike other electric boilers, you can easily replace a failed heat exchange unit...although we have yet to see one fail yet. The NextGen boilers also modulate in 1/3 increments. Perhaps give the Installation Manual a good read. It is truly a nice product expressly made for a clean and easy DIY trouble free hydronic radiant heating installation.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
Thomps0990User is Offline
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07 Jul 2022 02:23 PM
Thanks for the info,

I am going to reach out to some local propane suppliers to try and determine the total costs of LPG.
In addition to that Here in Ontario we pay a significant Hydro delivery fee, I need to add those costs into these calculations before I made a decision on the more cost effective fuel to be heating my home with.
If I choose the NextGeN I will mention the referral %100

Thanks
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07 Jul 2022 02:37 PM
Yes, research, plan and execute well! While I am not a big fan of mini splits, like Newbostonconst indicated, mini splits can be a great HVAC solution as it will only cost you about 1/3 as much to operate as an electric boiler and it can provide AC too. I am personally not a big fan of mini splits because I like simple devices that I can easily repair myself with simple tools and I don't like the look of mini split heads, feeling drafts or having a noisy compressor disturbing the remote natural and quiet tranquility of where I live. But from an efficiency and operational cost perspective, mini splits are the clear winner.

We use LPG for our kitchen stove, outdoor kitchen BBQ and patio Tiki torches. We just use a couple 100 pound tanks connected to RV style regulator that will automatically switch to full tank when other tank gets low. A tank lasts a couple years and this size tank is easy to take into town and get filled at significantly lower cost that having a truck come out to fill a large LPG tank. Plus I don't like the look of having a large LPG tank and we are in wildfire area too.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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07 Jul 2022 05:40 PM
I Actually recommended and installed a 36,000 BTU Mini split at my brothers home last week, What a breeze. I really like them and I was absolutely astounded at how quiet the outdoor unit is, Easily 10x quieter than his old window shaker. I had to walk within 3 feet and visually inspect it to see it was indeed operating when we first powered it up.

I intend to install one for AC in my build and some heating aswell.

I have done the deep dive into the air to water heat pump, It doesn't seem like the high cost of the unit and complexity of the install combined with a backup system for cold temps makes much sense to me financially.

newbostonconstUser is Online
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08 Jul 2022 12:22 PM
How do you plan on heating water for showers?

In summer we switch a couple valves and any water that enters the house goes through the floor piping first. This exercises the pumps and cools the house. So all water for grass watering, garden, and domestic use is used to cool the house and keep fresh water in the piping. Not normal but works for us. We are getting closer and closer to zero heating bills every year, we haven't paid an electric bill in 4 years, heating is going next.
"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
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08 Jul 2022 01:48 PM
Yes, eliminating all utility bills is the way to go!

We get all our water from one of our creeks and our well. Our grid electric heating bill is under $30/month for our 4000 SF of living space in our Southern Oregon house and shop using our electric NextGen boiler at our ACCA Manual J 26F 99% outdoor design temp and our $0.085/KWH electric rate. When we fire up our wood-fired masonry heater for about 60 minutes every other evening it heats house for 48 hours, our electric heating cost drops to under $15/month.

We will soon have hydro power via a cross flow turbine that will provide our heating season electric and photo voltaic for rest of year.

Our passive solar building cooling/heating design has worked exceptionally well and we don't need or have AC as a consequence and our house and shop indoor temp has never gotten over 68F under all Summer outdoor heat extreme conditions that often reach 110F.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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