Passive solar + hydronic retrofit - special needs!

Reyesuela_2 · July 2004

Here's the situation:

We're in the mountains where 45-degree fluctuations from day to night are common, and we have a six-month heating season, a two-month cooling season, and a four-month smug-little-SOBs season. *g*

Right now, we have a pellet stove and @#$% electric basebaord heat. I already know we want to go to an oil-fired hydronic system. Because of up-front costs of taking up all the current floor coverings and system installation plus future remodeling plans, it will start out as a mixed radiant floor and hydronic baseboard system. As we finish our remodeling, it will switch entirely to radiant floor (aluminum fins and sleepers method--low mass because of our day-night shift needs).

At night during the heating season, all the rooms will need considerable heat. But during the day, two 12x29' rooms get huge amounts of sunlight, and the heat is turned off at 8 AM when it isn't cloudy (most days here aren't). Then the upstairs passive solar room goes from 64 degrees to an average of about 80 degrees, and the rest of the upstairs usually gets up to 68. The downstairs room is more shaded, but it also sees significant gains. Meanwhile, the coldest part of the house (next to the pellet stove) goes from about 78 degrees down to 58 degrees. I work from home, never mind weekends, so this definitely puts a crimp in things!

Now, pretending that I've finished converting to radiant floors entirely...

I'd like to have the house zoned, especially since the hottest room during the day is the room with the greatest heat loss at night. I'd also like to have some way of circulating the water constantly between zones when needed to even out the temperatures. If I could do that, I'd be ably to be a lot more comfortable without heat! And, after dealing with the pellet stove for two years, I'd LOVE for it to be automatic.

First, is this possible?

Second, what type of boiler would be best for this application? (FYI, the boiler will be in a workshop conntected to the house, and size is not an issue. It will have an indirect HW tank attached.) I was thinking that a high-mass eutectic cast iron boiler like De Dietrich's might be better since it's made for constant circulation at a low temperature, but maybe a low-mass stainless steel would be better able to handle the fluctuations on demand.

Help!

jerry scharf_2 · July 2004

a real challenge

Passive solar is great, and it drives just about any heating contro system nuts. Even if it's low mass by hydronic standards, the mass of the floor system can still cause a major lag. I'm going to be playing with weather based predictive controls, but it's going to be very experimental and probably will go wrong at times.

I'm wondering if it is possible to use a whole house ducted ventilation system to mix the air and redeliver it. It may not be proactical in your house, but I would guess it's the most effective way to get the heat out of the hot rooms and into the rest of the house.

My gut reaction is that the heat recovery from the hot floor won't do it. If the floor in the hot room doesn't get above the water temperature needed to heat the cold room, the physics says no. If it's hotter, than it's an engineering problem.

jerry

Weezbo · July 2004

what you wondering about is doable.

however like giving bids over the telephone.... your in need of someone to be there..... and actually do this type of work for you. you are looking for someone who is into control stradgey...... a mechanical contractor who is familiar with intergrating systems.and someone who maybe rather adamant on specific requirements ,things need to be such and such and thats that. some things have some degree of flexability others do not. just from what you have said there are things that you dont find comfortable to live with and that is true for the person you hire too. he or she has a need to be able to stand behind thier work and let it speak for them. here at this site are contractors who may live near your area ,one of them would be a safe bet they take pride in thier work and big job or small they are happy to post thier work for further scrutiny by thier "peers"as it were. There are certain variables in this work that require a bit of accurate information and sometimes tests before undertaking the work. i hope you find someone nearby...there is find a proffessional on the menu ...calling someone direct to come out and take a look would save you alot of time effort and money in the future.
As a topic of discussion you can get twenty different answers from twenty different people how ever they would all have something in common,once done it would work right

good luck try "Find a Professional" on the menu.

Kevin_in_Denver · July 2004

Passive Solar without thermal mass

Did anyone warn you against having passive without sizing the thermal mass?

What do you mean by day-night shift needs? Why does that demand a low mass heating system?

Reyesuela_2 · July 2004

>Passive solar is great, and it drives just about any >heating contro system nuts.

Yes! Every time I show the heat load calcs to anyone and they gasp over the apparent heat loss of the solar rooms, I have to try to convince them how skewed the numbers are. *sighs* It makes a HUGE difference. We've never even used more than 50% of our heating ability for the "coldest" room, and that's when it was -26 degrees!

>I'm wondering if it is possible to use a whole house ducted >ventilation system to mix the air and redeliver it. It may >not be proactical in your house, but I would guess it's the >most effective way to get the heat out of the hot rooms and >into the rest of the house.

Short answer--no. *g* Can't do it. Lots of bare vaulted ceilings, no space to run ducts. Might be able to do something with an atypical application of a high velocity air conditioner in the future, but I want HEAT before I get a central AC!

>My gut reaction is that the heat recovery from the hot >floor won't do it. If the floor in the hot room doesn't get >above the water temperature needed to heat the cold room, >the physics says no. If it's hotter, than it's an >engineering problem.

I don't think it will get much above 90 degrees even in direct sunlight.

>Did anyone warn you against having passive without sizing >the thermal mass?

I didn't build it! This house's been here since '83. Don't get me wrong--the hottest room feels LOVELY in the winter--but it would be nicer to spread out the heat a bit (a lot) so that all the rooms could be comfortably warm rather that one toasty. No mater what, though, it definitely saves me heating money!

>What do you mean by day-night shift needs? Why does that >demand a low mass heating system?

From 9am to 5pm, the system should deliver as close to NO heat as possible, while at night, the solar rooms are the coldest, so it will heed to dump large amounts of heat into the room. If I had a passive thermal mass, that would be fantastic to even out the temps, but gypcrete/concrete wouldn't be passive--it'd continue to release heat into the room hours after it wasn't needed anymore.

>you are looking for someone who is into control >stradgey...... a mechanical contractor who is familiar with >intergrating systems.and someone who maybe rather adamant >on specific requirements ,things need to be such and such >and thats that.

I like working with nitpicky people. Heck, I AM one. *g* I wanted to have some idea of the kind of responses I can expect from someone who's being anal and nitpicky, though, in my area. Sadly, all the people up her who have retrofitted have gone to forced air with air-only contractors, so I don't really have any recommenations to start with.

jerry scharf_2 · July 2004

can you wlk on the floor in bare feet?

HI,

If you look at the R between the top of the floor and the pipe (the revese of the path up) you would need really hot floors to deliver enough BTUs into the water at 90 degrees. If you can walk on the floor in bare feet without discomfort, then it's probably below 95, and the BTUs available at 90 would be few.

I figured as much on the ventilation air. And I sure know what you're talking about in terms of trying to make a house work during a remodel. To say the heating was designed is to stretch the word.

How about making a kinetic sculpture that is a thermal mass transport system between the hot and cold sides of the house. Get some of the salts that melt at 85 degrees, put them in things that fly between rooms... Or a bunch of low pressure heat pipes that boil at 85 and run them through the walls...

good luck,

jerry

hr · July 2004

any way to

get some control on the passive gain/ loss? Sometimes money spent on operate-able shades can help get a handle on day time overheating and nightime loss back out that same glass.

As you have discovered too much of a good thing can lead to an uncomfortable and un-controlable "free heat."

Check into some "powered" shades or levolours (sp) possibly a tie in to a setpoint control. Storing and moving around this low grade heat can get pretty complicated and expensive when attempted hydronically. That's always been solars biggest challange both on the water and electric solar systems, where and how to store it

Still a fun energy source to play around with, let us know what you come up with.

hot rod

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Reyesuela_2 · July 2004

>get some control on the passive gain/ loss? Sometimes money >spent on operate-able shades can help get a handle on day >time overheating and nightime loss back out that same glass.

Acutally, I have some great insulated shades. When it gets too hot upstaid, I swallow my guilt and crack a window. *g* Just wish I weren't wasting it!!

>I figured as much on the ventilation air. And I sure know >what you're talking about in terms of trying to make a >house work during a remodel. To say the heating was >designed is to stretch the word.

HA! There is *no* central heat or air at all--for heat, there's just these terrible electric baseboard heaters that, with the solar, are sized wrong AND have no thermostats. There is a pellet stove, too, and a 9x9' HOLE in the bardroom (solar upper room) floor to let the heat through. For AC, there's a swamp cooler with a single big vent.

>How about making a kinetic sculpture that is a thermal mass >transport system between the hot and cold sides of the >house. Get some of the salts that melt at 85 degrees, put >them in things that fly between rooms... Or a bunch of low >pressure heat pipes that boil at 85 and run them through >the walls...

*giggles* Express my artistic side!

Kevin_in_Denver · July 2004

passive solar basics

"From 9am to 5pm, the system should deliver as close to NO heat as possible, while at night, the solar rooms are the coldest, so it will heed to dump large amounts of heat into the room. If I had a passive thermal mass, that would be fantastic to even out the temps, but gypcrete/concrete wouldn't be passive--it'd continue to release heat into the room hours after it wasn't needed anymore."

With all due respect, you really need to study up on passive solar. A good reference is Kachadorian's "The Passive Solar Handbook"

Reyesuela_2 · July 2004

>With all due respect, you really need to study up on passive solar. A good reference is Kachadorian's "The Passive Solar Handbook"

That won't do any good at this point. I know how it works, and I've taken (and aced) my thermodynamics.

The passive solar is in place. It's BEEN in place for 21 years. There is no large passive solar mass that would absorb heat during the day and release it at night. Sure, it would be nice, but it isn't there.

A high-mass floor would not absorb much heat during the day because during most of the day, the floor would still be hotter than the room. Energy travels from hot to cold, period. So during the time that (ideally) that big thermal mass on the floor SHOULD be absorbing all the unwated heat from the room, it'd actually be dumping it *into* the room until the two reach some sweltering equilibrium.

If the day's high is 20 and the low is -10, this would be the (rough) typical temperatures right now, with no radiant:

7:30 AM -- 65 degrees with the pellet stove at 3 downstars (30k BTU/h). Window shades get opened. Pellet stove is turned off--and actually goes off about half an hour later.

10 AM -- 68 degrees, no heat.

12 noon -- 72 degrees, no heat.

2 PM -- 77 degrees, no heat.

4 PM -- 81 degrees, no heat.

5 PM -- 78 degrees, no heat, insulated window shades dropped upstairs.

7 PM -- 74 degrees, pellet stove turned on low because it's 55-60 degrees downstairs.

9 PM -- 70 degrees, pellet stove cranked up.

11 PM -- 66 degrees

5 AM -- 62 degrees

So heat is needed from about 11 PM to 8 AM. If I had a high-mass system in the floor that shut off at 8 AM, it would be at about 82 degrees when it shut off, so it would continue to release heat that I didn't want for hours, just like a big thermal mass for passive solar but in reverse. (Which would be AWFUL.) When I wanted it to start heating the room again, I'd have a long lag while the floor absorbed massive amounts of energy before it could start heating the room.

If I played with the settings long enough, I could probably come up with a timing that didn't totally suck, but it would still be far from ideal.

So, yes, I understand thermal mass. And no, I still don't think the application would make any sense whatsoever.

Ken_8 · July 2004

Unless your budget and finances are

unlimited, I would use the KISS method rather than the somewhat exotic overkill direction suggested by others.

There are very few aplications where radiant is not only impractical - but a poor choice. This might be one of them.

Since I have no practical experience actually designing a solar anything (other than an awesome solar collector I designed and installed for our backyard swimming pool), I really don't have any input in that arena. However, radiant has one major weakness. That is, fast response to fast changing loads - either from sun loading, or fast and large outdoor temperature swings. Based on the parameters you mentioned, a well zoned HWBB system would be my first - and ONLY choice in this application.

600 BTU's / L.F. either upward temps - or down in less than five minutes, is about as good as you're going to get with regard to actual comfort and response times (And the two are directly related in this case).

If it's about comfort, HWBB would be my only choice in your rather unique application.

And when I rhetorically, up top of the thread, about financial resources, I was speaking both about the initial cost - as well as the over-time-operating-efficiency costs as well.

Would I recommend radiant in a tile floored bath or finished basement, or tiled kitchen area? - probably yes. But only in a near-the-surface, in-mud-under-tile application. Not fins on tubing under a sub-floor.

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Weezbo · July 2004

R U good at computer?

Take a look for the Gott'sBuilding in Sttutgard If theres a way ta doit they done it:) Green architect's are some creative batch. there must be volumes on remodeling Green buildings so they do in Fact work:) i think it wont be a quick read...

Weezbo · July 2004

R U good at computer?

Take a look for the Gott'sBuilding in Sttutgard If theres a way ta doit they done it:) Green architect's are some creative batch. there must be volumes on remodeling Green buildings so they do in Fact work:) i think it wont be a quick read...

Weezbo · July 2004

R U good at computer?

Take a look for the Gott'sBuilding in Sttutgard If theres a way ta doit they done it:) Green architect's are some creative batch. there must be volumes on remodeling Green buildings so they do in Fact work:) i think it wont be a quick read...

Weezbo · July 2004

Seems i double clicked somehow....

so,the air passes under the floor,to the cool side of the "exterior:"wall inside the cavity Provided by wall B and that exterior wall. this heat then heats the Building Redistributing the heat as it were...this is only part of the general idea............The Gotts building is fully intergrated. you read for understanding...then tell us what you feel is within the parameters of your physical,mental and finacial comfort levels. Remodeling is different..."Proper planning.... will avoid these problems in the future:)"good luck.

Unknown · July 2004

You could probably handle what you are looking for here with a combination of setback and/or outdoor reset features, with the outdoor sensor facing the direction of the first solar gain in the morning, in the first place hit by the sun. Then it would start backing the system down most quickly as the outdoor sensor warms.

A constant circulation mode to redistribute passive solar, however, as noted by others most likely wouldn't be too effective here; in all liklihood not worth the added cost and complexity of such a system at least.
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Mike T., Swampeast MO · July 2004

I don't think you'll be able to "move" the heat hydronically in the system you mention. You need either a LOT of low-temperature mass (both in the source [the rooms with the big solar gain] and the receiver [the rooms without the solar gain] OR a high temperature differential between the transfer medium (fluid) and the panel(s). You would appear to have neither.

You have to consider how the solar heat is coming into your space. Mainly the sun is heating the window glass and the glass then heats the space. But the glass (even though I presume there is a lot of it) doesn't really get very hot on the inside surface. It can only heat the objects in the space to some limited temperature via radiation. Since your main receptor (the radiant panel) doesn't have much mass, it quickly reaches its maximum temperature. Now the system turns mainly convective and the air overheats rapidly to its maximum.

You say there are high ceilings and no place to run ductwork. Is it possible to make an opening in an upper wall between the "sun" space and space deeper in the house, then install a simple fan inside the hole blowing air OUT of the solar spaces? As long as the solar spaces are quite "open" to the rest of the house you shouldn't have to worry about any type of return air.

This isn't to say that radiant floors are a bad idea, just that given the construction it seems impossible to move your excess solar gain hydronically.

IMHO if you do use radiant floors, the solar spaces must be individually zoned and carefully controlled. "Full" radiant floor heat may or may not be practical in the solar spaces and some form of operable window coverings may well be required.

jerry scharf_2 · July 2004

I'm with Ken, but a slightly different wrinkle

If you've decided to pass on the kinetic sculpture ideas, I'd ditch the radiant floors in the main rooms.

I would personally choose some nice panel radiators over HWBB. They both shut down nice and fast, but given the vaulted ceilings and glass walls, I'd prefer to keep the convection to a minimum.

I'd also do a few things with controls. I'd motorize and computer control those insulated drapes, and even allow it to close in on the sides a bit if the temperature starts to overrun. I'd also look at what kind of set back and recovery could be done. With all that glass in an unused room at night, you could probably save a bunch by letting the room drop off 10 degrees at night. It then becomes an issue of the recovery time to make the room habitable on a dark winter morning (I've heard that you have some of those even in the Rockies.) A modulating boiler seems very valuable for effeciency in this setup.

I'd give the tecmar controllers a serious look, but you have to make sure you have an installer that can handle the technology and will stick with you to get it all working well. I guarantee that any control system will take some tuning in a difficult situation like yours.

best of luck

jerry

Passive solar + hydronic retrofit - special needs!

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