iDRY Vacuum Kilns

Sponsors:

Radiant heat vs. TF with SIPS

Started by bigshow, March 08, 2008, 04:12:16 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

bigshow

Folks,

I have found a couple radiant heat contractors locally that have actually won some awards for radiant heat installs, design.  One seems really easy to work with - even not having a problem with me doing as much as i'm comfortable with.  The other is hesitant to do radiant in a house that is too well insulated.  Stating that it'll be overheated..i'm thinking, then dont space Pex as close together.  I know i'm priced out with the contractor that wouldnt be my first choice (25-50k for 2k sq ft).  I HAVE NOT submitted my floor plan and details to either contractor yet...so i have no real numbers.  Its not looking good.  Anyone here in a northern climate using radiant as primary heat source?  cost of install? impressions?  do you feel its more efficient than forced air? 

thanks for any info anyone can provide.....
I never try anything, I just do it.

krusty

Huh? I would get rid of the second one. There is no such thing as overheating a house if it is properly designed. That is the whole point for a good design!

I am currently installing in my TF/Log house and have one room up and running....so far so good! But if you really want to DIY I suggest the hydronic text available off of Amazon.

The other thing....I used HTP under the subfloor and next house will to a 1.5" embedded concrete on all floors for better efficiency.

You really cant compare radiant heat to other forms.....and the text provides a good discussion on it. And to put it into perspective.....go have a bonfire outside on a cold nite....as you are next to it, the air around you is still cold, yet you feel warm.....and cozy. That is radiant heat 8)

bigshow

'hydronic text'?? is that the title of the book, i did a google search and no exact match.  I suspect your referring to " Modern Hydronic Heating for Residential and Light Commercial Buildings"??
   


thanks..
I never try anything, I just do it.

Dave Shepard

Maybe I'm all wet, as some of our members would say, but 25 to 50 thousand just to heat two thousand square feet?  :o :o :o :o I don't see how you could be overinsulated. If the room gets up to temp quicker, won't the thermostat shut it off, or as you say, put less tubing in so the heating cooling cycle takes enough time for the t-stat to react? I don't know how much of your own plumbing you can legally do, but I'd go for it. I have helped on a couple of radiant projects, and it goes in pretty easy. It is really popular around here. We can get plenty of cold weather, but I don't know what a South Dakotan's idea of cold is. :D


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Don P

When I was working there one winter a Canuckian came down to see what it was like in the south  ;D.

Our tf owner put in a "boiler in a box" from AIM radiant. It was the first radiant I've been around to any extent. It seemed simple and seems to work well. I don't know that I consider it super efficient but have nothing to really compare that to. As it gets colder we can overheat the slab basement without being able to get as much heat upstairs over the wood floors as I would like. There is radiant in both floors but I do think in a good design the designer would have known how to properly distribute the tubing to better balance the system. We are still playing with different things and I think will be able to tip the balance. With a colder exterior I don't think we could as we are built now. Long way of saying your situation is more demanding, I'm running out of "pedal" upstairs although I can bump the water temp higher, I don't want to if possible under the wood floor. I also think our basic plan is maybe not as good for radiant upstairs. Tall cathedral, lotsa glass, windswept lot, it is in Sips and tight. The house sets up convection currents in the tall center of the house. There is cool air dropping down the glass and the rising warm air is warm, not hot. We tend to be used to a column of very warm rising air in a forced air system. Over wood and/or in a tall room I'm not sure I'm as happy.

krusty

Bigshow....you got the right book.

Heat loss calcs are pretty straighforward. I have a little manifold that feeds water to each are of the house as needed. Each of those areas has its own thermostat. Valves turn on or off to let hot water heat as needed.

I am using propane out in the country and a tankless water heater.

Prices so far.....

$2500 water heater (which can do domestic water as well)
$2000 hydronic parts
$1500 in aqua pex tubing

$300 in making my own heat transfer plates

$1000 insulation approx

and this is for a 1500 sq ' house

DouginUtah

Quote from: Don P on March 09, 2008, 12:02:47 PM
As it gets colder we can overheat the slab basement without being able to get as much heat upstairs over the wood floors as I would like. There is radiant in both floors but I do think in a good design the designer would have known how to properly distribute the tubing to better balance the system.

Don,

I don't know what your system on the first floor is (poured in grout or under floor PEX), but it sounds like you need a Tekmar valve--if you can bump up the temperature at the first floor. The basement slab should not be over 140° but maybe you can go higher upstairs. If the basement is too hot, adjust the Tecmar valve to put less heat there. There is a picture of mine in my photo gallery.

-Doug
When you hang around with good people, good things happen. -Darrell Waltrip

There is no need to say 'unleaded regular gas'. It's all unleaded. Just say 'regular gas'. It's not the 70s anymore. (At least that's what my wife tells me.)

---

Thehardway

Bigshow,

Can you supply us more details?  How far along on this project are you?  What type of floor are you planning on having? concrete slab, wood, and what kind of floor covering do you plan to have?  Contractors charge a premium for radiant because it has historically been considered the cadillac of heating systems.  Recent developments such as PEX tubing have made radiant much easier and DIY friendly.  25K for that space sounds very high to me. 50K is outrageous.  Sounds like they have allowed a good profit margin and quite a bit of CMA factor. They are probably charging you as well for there award winning accolades which may or may not do you any good.  Sometimes contractors price jobs by how much they think the owner is good for.  If you have a custom home or are in a wealthy area they will overcharge and tell you that they are the best.  I get this a lot as I am in lake subdivision. 

There are a couple tricky things to radiant I have learned from those who made mistakes.  Radiant is not as quick in response time as a forced air sytem because you are dealing with thermal mass.  It takes a while for things to heat up and even more time for things to cool down.  This is exaggerated in homes with extermely tight envelopes or insulative type floors (carpet or thick wood).

Example.  Your home is nice and comfortable with floors at 89 degrees and ambient indoor air temp of 68.  You decide to bake some pizzas and have some frieinds over to watch a race. The oven raises the air temp in your tightly built SIP/TF home to 74 and your friends arrive shortly after.  The additional body heat and humidity raise the room air temp to a sticky 76.  You turn back the temp on the thermoststat but it will be at least an hour before the floor temp drops so you end up having to open windows to cool it down. About the time your guests get ready to leave it is down to a comfortable temp but now it is night and your floors are below temp and the air drops to 64 with no guests.  Now your back to the T-stat turning it up but it won't be back up to temp for another hour or so if you are lucky.

If you have not lived with radiant heat before it can be difficult to get used to leaving a T-stat alone and manipulating other factors in the room to control air temp.

Temp Response times can be enhanced by increasing the size of your tubing and decreasing the insulative properties or mass of your floors. This can however, decreases the energy efficiency of the system. Mixing valvess can put cold water in the pipes to accelerate cooling if neccessary.  A good ERV can bring in cool outside air in emergency.

If you are going to use radiant, evaluate your building materials and optimize them to work with you.  For floors with good conductivity and thermal properties like an insulated concrete slab and ceramic tile, water temp may never need to go above 90 allowing you to use a standard PEX pipe and a standard hot water heater. This is a very efficient design and works well.

If however you put down heavy padded carpets on suspended wood floors over a crawl space or basement you will find yourself needing 120+ temps and "running out of pedal" the pumps will never shut down as there is no mass to hold the heat and your house will probably feel a little cool most of the time.  You will need a very expensive boiler and will need oxygen barrier pipe, both of which will add to the system cost.

These occupant based variables are just a few of the things that make most contractors defer to standard forced air systems in spec. homes rather than radiant systems.  This is also what keep te cost on installed radiant systems high as volume has never had a chance to enter the market and drive down cost.

Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

bigshow

only thing that is done: Frame design.

I havent decided on the foundation.  I really, really wanted to have about 1/3 of the main floor be a concrete slab, since i designed it to be passive solar.  I later learned from a timber framer that i respect very much..that a passive solar slab + radiant in that slab is a bad idea.  I dunno...i have a hard time digesting it.  put that slab on its on thermostat...if it heats up during the day..no reason i have to keep pumping hot water through it.  Most of the rest of the house will be hardwood, tile, and little carpet (i took all the carpet out of my current house - wife and dogs allergies vanished).  I was thinking sandwich construction: subfloor, nailers on top of that for aluminum plates with channels for pex, and hardwood over that.  I'd want some areas to be in floor (most of main level, basement, bathrooms), and the sleeping areas i was thinking radiant baseboard type configuration - which i was told adds a great deal of complexity. 

If i do a full basement...i'm gonna end up with WAAAAY too much house.  those are my thoughts so far.

all opinions welcome..the discussion so far has been helpful.  And of course, I do not have real world quotes yet...but nothing wrong with gathering info.
I never try anything, I just do it.

Thehardway

Bigshow,

This info is helpful and revealing. IMHO the reason your qoute is high is probably because you have so much going on.  I would try to simplify before taking for a final quote.  I agree with your TF friend in part.  Using a passive solar slab and having  radiant in it raises some issues.  Example:  If your temp sensor is in the floor, when the floor warms and satisfies the set point on the t-stat you will be shutting down the non-warmed areas  as well.  A system like this requires multiple zones with multiple sensors. Once again this adds to the complexity and cost although it is not impossible.  The scenario you describe requires lots of different water temperatures as well which means lots of valves and controls.  It would probably require a computer system to control the system and keep it balanced. It would probably take 2 years or more to pattern it for seasonal changes and get everything fine tuned.  I DIY would be near impossible unless you have lots of engineering background and lots of time and patience.

I am a big proponent of radiant in slab but only if it is properly insulated and thermal breaks are installed for zoning.  This is very important if the system is to run efficiently.  Passive solar for slab works best if the area is not directly in the living space.  A solarium or sun porch work well because the room can be closed off of it becomes too hot or too cold and heat or cooling can be taken off in a controlled form.  Putting passive directly in the living space requires that you design some control elements into the home to limit the effect of seasonal change.  Solar orientation is very important in this design as are overhangs on southern exposures to limit summer heat gain while allowing winter. Often window films or awnings become necessary due to too much heat gain and the house becomes dark and dreary during daytime.  Recognize that glazing which allows heat gain in the daytime is a very poorly insulated area and you will lose a large amount of heat at night through glazing.  It defeats the purpose of a super-insulated home to put too much glazing in the living space unless it can be isolated.

Passive solar can be applied directly to hot water heating through an evacuated tube collector or a flat plate collector rather than slab heating.  The water can then be used at will.  Evacuated tubes are very efficient and can heat water to boiling even on cloudy days in the winter.  If a large thermal storage mass is used with this you can literally go for up to a week without significant sun and still have a comfortable home.

Recommendations from an idiot:

1. Simplify the design to include no more than two types of radiant mediums
3. Design for lowest possible water temps
2. Use passive water heating rather than passive slab
3. Incorporate an isolated thermal storage mass into design
4. Decide if you are trying to save money in construction or maximize comfort and efficiency for long term gain
5. Always design for a backup just in case.






Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

bigshow

Hardway,

Ok, you got my attention with passive water heating.  You have any good online resources/and or books to point me to?  I've been trying to find how it would perform in a cold climate - no concrete answers yet.  So, if you go passive water heating + radiant heat - Does the house orientation matter anymore if you ditch the slab (obviously the water tank is properly orientated)?  I am in one of the windiest areas in the country - and i think little wind turbines would be awesome (pretty expensive, turbines are not - towers are)...but being able to heat water with the sun would be a good start.  But, depending on how much the cost of adding passive water heating is...i mean, electricity for heating/cooling for me is 4.25 cents Kw/h...gotta consider pay back too....
I never try anything, I just do it.

EastMark

You know this whole radiant/passive solar/etc thing is pretty specific to the layout etc as we see from these examples.
I have decided to hook up with a Resdential EnergyStar Certifier to go over options on my house plans.
I understand they will help analyze options and their payback timeframe as well as even more importantly...comfort.
I am doing all the hard stuff toward certification already...SIPS,Hi Effeciency heat,Hi Eff windows,HRV System,etc so why not get someone involved that does this daily and get the house EnergyStar Certified I figured. I dont want a very effecient house with uneven heat or another issue.
They will help with placement of windows,sizing of systems,placement of vents,payback times,etc on the plans....come out once during building to check specs, and then do the blower door certification and rate it. Yes they do the blower test on a SIPS house.
I think the $750 is worth it. The house will probably be worth that much more plus...and there are rebates availible for getting rated. I'll let you know how it all goes...good,bad, or ugly. ;-)
Mark   

Thehardway

BigShow,

The oreientation of the house is not critical when using passive solar hot water, nor is the orientation storage tank.   The only thing that must be properly oriented is the collectors. The hot water is circulated through these and then stored in an insulated tank which in many cases can be buried or placed in a small shed.  Usually a glycol solution is used to prevent freezing and boiling. Evacuated tube collectors are built like a thermos bottle. A vacuum separates the water circulation portion from the air. This make them extremely efficient in cold weather, and prevents heat loss at night.
Using solar energy to heat water is probably it's cheapest and most efficient home solar application.  Hot water can be run through fan coils and used to supplement a forced air system although the heat transfer is not as efficient or comfortable as that provided through radiant floor heat.  When looking at costs, evac. tubes may appear high but in many cases used ones can be obtained at a reduced price.  Additionally a tax write off can be taken for the purchase of them which offsets much of the cost.  They will provide virtually unlimited free  domestic hot water for you during the summer months whereas a passive floor in the home would do nothing for your power bill in the summer.
Google "Evacuated tubes" and you will find lots of info on the various types and info available.  Mother Earth News and Backwoods Home magazines often have articles on them as well as suppliers and advertisements.  They are popular in off grid homes.

As I stated before I'm not a pro on this by any means, just passing alon info I have gathered, and Mark's advice to get professional assistance is very prudent.

Mark,
I like the Energy Star program but feel it falls short in the following area. All the Energy Star Home label does is verify that your home is at least 15% more energy efficient than a comparably sized home in your area built to the 2004 IRC minimum standards for energy efficiency as dictated by the EPA.

The criteria is based on a computer simulated model.  Once again, like R-values, this is not a real world performance rating but rather a calculated performance.

To their credit if performed properly the blower door may really evaluate how airtight the construction is, as does the duct pressurization test the Energy Star raters perform, but once again the actual performance of the home as a unit is based on labratory  tests of window performance, R-values of insulation heating and cooling systems etc. and the final Energy Star rating is strictly a comparison rating.  In reality a SIP /TF home will likely be 15% more efficient than any stick and batt home built to any code on day one regardless of the windows, ducts and heating methods used.

For this reason I like the HERS rating system or LEED approach better as they are more inclusive.  LEED trends toward the tree hugger side a little much in some areas and can be manipulated but I like how it takes into consideration landscaping features, air-quality and energy efficiency, water usage etc. all of which affect total home performance and your net utilities bill. 
 
You may know in many cases special mortgages can be obtained by using any or all of these programs so your $750 is more than covered and you can also get a healthy tax deduction. 
Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

EastMark

Hardway,
The group I will use does use HERS ratings/testing and will rate the house that way. They also aid you in getting the rebates paperwork in order. Interesting thing (not sure if its just Maine) is he told me the $2000 rebate out there is only availible to 'builders' and not a homeowner that is acting as their own GC. Thats good info and I have options to cover that now that Im aware of the hurdle. I hope they have success in changing that eventually. There are other rebates out there for solar use,etc besides.

The Maine program is rumoured to include alliances with the Gas company for discounts the first 2 years,some insurance companies offering discounts,some banks participating in mortgage discounts...all based on the theory that a Energy Star rated house would be 'less of a risk' than the average home.
You surely forgot more than you know about the systems and the outcomes so I feel good about using this guy to guide me based on my specific plans. Comfort and ease of use is critical to me.

This EnergyStar rated stuff is only going to get bigger in years to come. Oil is over $109 a barrel today !

Mark

EastMark

As a side note, we had a very brief discussion about radiant and the fact that I had a small Glenwood Parlor stove I would like to use on occasion as a novelty. He suggested that he needed to reveiw the whole house plan,but that its possible this fact combined with 23 foot ceilings/half house loft area may make baseboard a better fit but said he would reserve judgement until he reviewed it all at our meeting.
I like/want the radiant but am open to ideas from him. It has to be comfortable not just effecient. If I go baseboard I am going to have to find some type of covers for the units that blend with the older look we want. I googled and spotted a few that arent horrible.

Mark

bigshow

I've been looking all over for LEED accredited pro's, and the like - cant seem to find an all in one person...looks like for LEED you have to have a building engineer, mechanical, electrical..which makes sense..cant be a master of everything.  I think i'm gonna call my electric coop and see if they have resources.  Lotta good ideas in this thread though....
I never try anything, I just do it.

Thank You Sponsors!