Tricky radiant design requirements for a vacation home

Vahson_Dan · October 2011

Hi Everyone, 

I’ve been all over the internet in the hopes of nailing down a great design for a 2500 vacation home. Several sites point to this being the place to be. Here’s the framing of my desires:

 

New construction (not yet built) of a 2500sq ft home

It will be well insulated.

Two floors with lower being slab on grade and upper being concrete slab on trusses

Natural gas heating source would be used.

I’m looking for something reasonable; not a ‘Street of Dreams’ home design point

 

DHW is needed for 2 bathrooms

DHW system should have a “Disable during away” option via relay.

 e.g.: Tekmar 400 series controllers offer this.

 

Controller system should have a “Enable setback” option via relay. 

 e.g.: Tekmar 400 series controllers offer this.

 

Floor plan warrants about 5 zones: Main lower living area (incl one bathroom); main upper living area (incl one bathroom); master bedroom (west facing with large windows); two lower bedrooms (west facing with large windows)

 

I can’t ever turn off the water due to my being required to have a fire sprinkler system so I’d like to be able to power the system during an extended outage with an inverter standby system (battery powered). This means fewer pumps; possible use of zone flow control vs zone pumps; more power efficient pumps (at least when on battery power); and a boiler that also does not need too much electricity.

 

Given all of the above, it’s been too much for me to figure out. 

 

What I’ve discovered thus far: 

1) Tekmar 400 series controllers seem perfect for the above

2) There are many type of boilers (combi, on-demand, specialty) and the rationale to use one over another given the above) is far from obvious (to me!). e.g.: 

a. Basic units like the Viessmann Vitodens 100-W condensing boiler 

b. Triangle tube Prestige Excellence with 14 gallon in-cabinet indirect fired water heater 

c. Laars Mascot II with internal DHW heat exchanger with priority for on-demand hot water

Any and all guidance is much appreciated!

LarryC · October 2011

What are the planned heat emmitters?

What are the planned heat emmitters? Concrete slabs sounds like you might be planning radiant floors. Correct?

What are the expected time lengths that the house will be occupied or not occupied? High mass radiant will take some time to come up to temperature from a setback. Time frame could be a few hours to a day or so.

Steam with radiators or cast iron haseboard have no pumps, minimal electrical demand, and low water content. They can run on natural gas with the correct burner. Small radiant zones can be connected to the boiler if a small zone is wanted.

What part of the country is this place going to be located? Is the elevation higher than 2000 feet above sea level?

Vahson_Dan · October 2011

Tricky radiant design requirements for a vacation home

Hi Larry

What are the planned heat emmitters? Concrete slabs sounds like you might be planning radiant floors. Correct?

>>> PEX in slab for both floors. Heating source itself is something I'm flexible on. Efficiency (both gas and electricity) is more important than cost.

What are the expected time lengths that the house will be occupied or not occupied?

>>> Weekdays out, Weekends there. I will 'call in' to remove the floor setback say a day prior (from 60F to 70F), For DHW setback I can call in far later.

High mass radiant will take some time to come up to temperature from a setback. Time frame could be a few hours to a day or so.

>>> Agree, per above I'll wake them up independently and also set the lower temp accordingly.

Steam with radiators or cast iron haseboard have no pumps, minimal electrical demand, and low water content. They can run on natural gas with the correct burner. Small radiant zones can be connected to the boiler if a small zone is wanted.

>> I'm deeply interested in warm floors (radiant). Otherwise I'd go with a minisplit and call it done.

What part of the country is this place going to be located? Is the elevation higher than 2000 feet above sea level?

>>> Seattle, WA @ sea level

Thanks for the reply and future thoughts!

CMadatMe · October 2011

Simple

Based on thenlimited information water temps for the radiant would only require one temp. Vitodens 100 is a goodn choice of boiler. Could use the Uponor Climate Control Network, have internet access to call up the system and even have it call you if any problems arise. Boiler can be run by an outside source without taking away the boilers firing logic. Your only telling it what system supply or dhw temp you want. Simple and cost effective. Taco I-Worx is also another good internet based system that will do what you want.

The key is going to be finding the right installer.

LarryC · October 2011

DHW setback concerns

"I will 'call in' to remove the floor setback say a day prior (from 60F to 70F), For DHW setback I can call in far later."

Be carefull about the DHW setback. Legionella bacteria LOVE low temperature (warm but not hot) water. Ask Mark Eatherton. He has first hand experience with it.

With the low duty cycle that you are expressed for house heating, 5 off 2 on, plus the use of a high mass heating emmitter, solar thermal might make sense. Collect heat during the week and use it for the weekend. If the house will be very well insulated, the only demand load will be the domestic hot water.

Minimal or no setback on the floors, store the low flow high temperature water for domestic hot water, backed up with a smaller water heater to supply what could not be met by the stored heat.

A drain back system will automatically turn off the solar system when the maximum heat is collected, a decent sized UPS can back up the entire system, and you will be heat mostly self sufficient. A small system connected to the NG system will provide backup.

A different approach would be a combined heat and power system that connects to the gas system. A small engine generates electricity and produces heat for domestic hot water and space heating. As long as the gas supply is reliable, you would not have to worry about freeze issues.

LarryC · October 2011

DHW setback concerns

"I will 'call in' to remove the floor setback say a day prior (from 60F to 70F), For DHW setback I can call in far later."

Be carefull about the DHW setback. Legionella bacteria LOVE low temperature (warm but not hot) water. Ask Mark Eatherton. He has first hand experience with it.

With the low duty cycle that you are expressed for house heating, 5 off 2 on, plus the use of a high mass heating emmitter, solar thermal might make sense. Collect heat during the week and use it for the weekend. If the house will be very well insulated, the only demand load will be the domestic hot water.

Minimal or no setback on the floors, store the low flow high temperature water for domestic hot water, backed up with a smaller water heater to supply what could not be met by the stored heat.

A drain back system will automatically turn off the solar system when the maximum heat is collected, a decent sized UPS can back up the entire system, and you will be heat mostly self sufficient. A small system connected to the NG system will provide backup.

A different approach would be a combined heat and power system that connects to the gas system. A small engine generates electricity and produces heat for domestic hot water and space heating. As long as the gas supply is reliable, you would not have to worry about freeze issues.

LarryC · October 2011

DHW setback concerns

"I will 'call in' to remove the floor setback say a day prior (from 60F to 70F), For DHW setback I can call in far later."

Be carefull about the DHW setback. Legionella bacteria LOVE low temperature (warm but not hot) water. Ask Mark Eatherton. He has first hand experience with it.

With the low duty cycle that you are expressed for house heating, 5 off 2 on, plus the use of a high mass heating emmitter, solar thermal might make sense. Collect heat during the week and use it for the weekend. If the house will be very well insulated, the only demand load will be the domestic hot water.

Minimal or no setback on the floors, store the low flow high temperature water for domestic hot water, backed up with a smaller water heater to supply what could not be met by the stored heat.

A drain back system will automatically turn off the solar system when the maximum heat is collected, a decent sized UPS can back up the entire system, and you will be heat mostly self sufficient. A small system connected to the NG system will provide backup.

A different approach would be a combined heat and power system that connects to the gas system. A small engine generates electricity and produces heat for domestic hot water and space heating. As long as the gas supply is reliable, you would not have to worry about freeze issues.

Tim Potter · November 2011

Question 1

Dan, How important is it to have hot water the very instant you arrive ? or could you wait _____? minutes?

Your house sounds like a larger version of my vacation house. We have 2000 sq FT at 9000' elevation in Colorado. We deal with the same issues, how do I get the house warm for our arrival.

Tim

Vahson_Dan · November 2011

Reply to Tim

Hi Tim,

Thanks. Waiting for DHW is not a problem. We turn off our natural gas DHW tank today when we leave and then turn it way up to 'sanitize' the water. The key was understanding how best to setup a setback system. General offline feedback was that with a 4" slab I'm not going to save very much letting the temp drop given the time it takes to fall and then to climb back up.

By the way, I've since connected with someone offline for some design work. I'm in good hands now.

Mark Eatherton · November 2011

Hydronic Solutions...

That would make a great company name eh...

Instead of cement upstairs, consider Warmboard. Fast response time for the lowest operating fluid temperatures.

As for logic, look into ENV by Climate Automation Systems. I have it in my cabin, an hour further west than TIms cabin, and I can turn EVERYTHING up or down from teh internet, including from my iPhone. And I can program it such that if it should happen to experience a problem, it will send me an email to let me know something is amiss before I start freezing and breaking things.

For the main floor, consider Warmboards R panel for radiant ceilings. I have it in my cabin, and it works fantastic. And if the wifey decides she wants to cover the floor with bear rugs, she can do so without me getting upset about the R value of floor coverings, and the response is FAST. Ceilings can put out more BTUH than a floor.

If you have a bathing facility on the main floor, consider using electric radiant floors only in that area. That is truly where radiant floors are a must. Everything else can be done with radiant ceilings, and still deliver excellent radiant comfort, AND you could do radiant cooling in those areas with radiant ceilings.

Just food for thought. Everyone is so enamored by radiant floors, when in reality, radiant ceilings cost less and work better in delivering radiant comfort.

ME

Tim Potter · November 2011

Glad to hear you have a designer...

Glad your using a designer, you only get 1 chance to do it right, on my house, they only got 1 chance to do all the piping wrong...

Thanks to Mark Eatherton and others on this website I was able to correct all the wrong piping at my house. Big Job though.

The response and ideas from Mark Eatherton should be taken VERY seriously, use him for a reference to steer you in the right direction. I'm sure he can help you. I've had him up to my house, well worth having him on your TEAM

Let us know how it works out,

Tim

Mark Eatherton · November 2011

Thanks Tim...

I appreciate the referral. You still need to come by the long, long LONG reservoir for a beer.

ME

Vahson_Dan · November 2011

Getting it right the first time...

Yeah, agree. I'm working with Paul Pollets of www.advancedradiant.com. If I look around I can see that he's a regular PITA around here . Kidding aside, after reading John Siegenthaler's book and then chatting with Paul for 30 minutes I suspect that Paul forgets more about radiant technology in a given day than I can ever learn. I feel in good, no great, hands. I just hope he does not charge me too much

Mark Eatherton · November 2011

You are in good hands...

Paul is an ARTist who paints with torches and pipe wrenches.

Keep one eye on the parrot...

ME

Sal Santamaura · November 2011

Warmboard R as a ceiling installation

Mark, that's something I was wondering about recently. How do you mount it up there? Type/amount of insulation above? Attachment of drywall below? Water temperatures? Any other tips? Thanks!

Mark Eatherton · November 2011

Screw it...

to the ceiling trusses just like you would sheet rock. Then screw the sheet rock to the Warmboard. No problem seeing where the tubes are...

SIggy recommends 1/2 gain as much insuation than would normally be required, but I've seen it done with a LOT less insulation (think 3.5" rockwool, 70 year old operation) and seen it still work. THe more insulation, the lower the operating temperature and costs.

I run mine at 140 at design (-15F) conditions.

Whenever possible, use non electric TRV's. THe energy consumption is proportional, and semi- constant below 40 F outside, except when solar influences kick in during the afternoon.

I also operate my system based on a sensor within the space with my ENV logic. I keep the place at 40 degrees F when I'm not there. The TRVs are just there to govern the upper temperatures.It is set so that it is just shy of satisfying the set point of the ENV logic. 70 vs 68 on TRV.

I've been running my windows at 72 degrees, and it is working great. I'm getting ready to start some experimentation with the windows. If I leave them on, and they run 24/7, it would cost me about $60.00/month. Will have to see what influence the windows have on the rest of the house at design conditions...

But I digress:-)

Personally, I think radiant ceilings are one of the most overlooked potential that there is in delivering excellent radiant comfort. The floors actually get warmer as it gets colder outside due to the ceiling getting hotter and also sending energy to the floor. In a properly controlled situation, most people can't tell where the energy is coming from. Their bodies can just feel the higher MRT, hence comfort.

ME

Tricky radiant design requirements for a vacation home

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