Radiant Heat and air conditioning ????

Jim_19

My wife and I have begun the process of sketching out a new single story home for retirement living. The design will include 100% radiant heat. Living in New England, we only need air conditioning for a month or so every year. But, when you need it, you need it!

What should we be incorporating into our plan to meet this need? Window air conditioner? Some small central air unit? We're still at the pencil and paper design stage so we are open to virtually all the options. What have you seen that was successful?

Thanks.

GMcD

Radiant heating and radiant cooling

Given that your climate only requires cooling for a short period, plus some dehumidification, I suggest looking at improving the selection of the windows and exterior shading to reduce the cooling load in the rooms to under 12 Btuh/Sq.Ft. and use the radiant system for the primary cooling. To ventilate the house, use an air to air energy recovery unit (Greenheck, Venmar, LifeBreath) with a supplementary heating and cooling coil on the main supply air duct to the rooms and you can do most of the steady state cooling via the radiant system, and then do some de-humidification and peak cooling shaving with the air side. An air to water heat pump unit might be a suitable energy plant, or geothermal heat pump, or a small air cooled water chiller with a high efficient boiler set. Just gotta get warm water and cool water flowing through the primary side to get mixed water to the secondary zones

It's all about the building envelope, the more attention is paid to the envelope, the lower the energy use, and smaller the house heating/cooling plant will be.

Empire_2

Unico Hi Vol. Unit

This unit for ac will provide A/C for the single story home with minimal clearance space. Need some room to work as it incorporates duct, ( small as it may be) to serve every room Can be installed in the attic or Under main floor. I think the web sight is Unico.com.
Good luck and Dont hide your equipment in a tight space, because the service men are not snakes. Meaning please allow adequit space for future servicing of the equipment.....LOL..
Also in closing, do you want to spend 8000,00 or 18,000?
Upper message is great, but it's up to your personal budget.

Jim_19

So, if I understand you correctly, you would suggest driving cooler water through the radiant system for "primary cooling". What extra equipment (if any) would be needed at the boiler to handle that? Since the boiler produces hot water and the mixing valve(s) reduce the temperature to that required by the slab can I assume that the mixing valve(s) have a cold water line attached? And that the cold water can be used to cool the slab?

Again, if I understand you correctly, when you refer to "main supply air ducts" you're talking about essentially installing a ducted heating/cooling system and using it for the peak cooling needs.

As a homeowner I'm hoping to find ways that would not require a duplicate system. It may be a pipe dream, but I'm hoping! Thanks for taking the time to educate me.

Jim_19

www.unicosystem.com

Found it under www.unicosystem.com Lots of interesting reading. From what the site claims, it looks like less ductwork than a traditional whole house system. And it also looks like an easier install.

What does the installation cost run for a typical single floor home for new construction? Ballpark - is this the $8,000 you mentioned or the $18,000?

Thanks for the information and your time.

GMcD

Radiant systems basics

In any radiantly heated (and cooled) space, there is still a need for a ventilation system: make-up air for washroom and range hood exhausts, etc., plus to remove humidity generated by the occupants and other sources, and to de-humidify incoming fresh air. Therefore all tightly constructed new buildings need a ventilation system regardless of the heating and cooling method. The required air circulation for the straight "ventilation function" is a lot less than the air required for heating and cooling functions. The lowest capital cost system is obviously to use the ventilation system to also provide a bunch of hot and cold air to perform "triple duty" - heating temperature control, cooling temperature control, and the ventilation function. We all know the comfort issues, duct space issues, and energy use issues associated with that type of "all-air" system.

To perform hydronic heating and cooling with a radiant system, it is quite easy to set up a primary/secondary pipe and pump system so that the primary side water switches from heating to cooling based on the season, and then the secondary pump circuits mix the desired water temperature for the radiant systems/zones. Primary cooling water or heating water is also directed to the air coil in the ventilation duct(s) for supplementary heating or cooling as needed. The boiler and the water chiller (or a single water source heat pump that provides both heating and cooling water) can be connected to the primary water circuit and enabled/disabled based on the season/outdoor temperature. The risk is that there are very few Contractors who will take on the challenge of the radiant cooling side of the system. Look at it this way- you already have all the tubes in the building for radiant heating anyway, why not make full use of them to do some cooling as well?

The advantage of this type of system is a very small ventilation system (that is required anyway) while the radiant systems provide the bulk of the heating and cooling space temperature control/comfort control. No duplicate systems - the radiant systems provide almost all of the basic comfort control, and the required ventilation system can be used to add a little bit of peak heating and cooling when needed.

Domestic hot water generation, which is needed year round, is best done with a separate heater, and not part of the building heating/cooling system, unless some kind of hydronic heat pump system is used with a boiler back-up.

Constantin

Have a look at the Karo system...

... which can be found at Natural Cooling.com. It's a ceiling radiant heat and cooling system that provides very good heating capabilities and adequate cooling capacity as well.

It consists of a web of capillary tubes that are embedded into the ceiling. There, they work with the plaster to keep your ceilings hot or cold, depending on the season. Any crown molding will hide the manifolds that feed the capillary tubes. Dew point sensors recognize whenever someone leaves a window open and shut off cooling before condensate forms on the ceiling.

The only downside to ceiling radiant heat is that areas where the radiant energy is blocked by objects (such as the area under a table) will feel cool. Plus, there aren't as many residential AC installers that know how to tackle water-based jobs... Having said that, once you find the right installers, the rest is easy.

As was stated higher up, even with a radiant cooling system you will still need a minimum of ductwork to keep the air quality up and to remove any latent heat (i.e. humidity). However, considering that in our NE climate the average ratio of latent vs. sensible heat is like 10% vs. 90%, you get an idea by what order of magnitude the AC ducts, etc. can shrink when you go with radiant cooling.

I seriously considered it until timeline pressures on our renovation job basically dictated going with the traditional approach, as I was not able to find anyone in the Boston area who had actually installed radiant ceiling systems before. Thus, we have radiant floor heat combined with a traditional AC system, a tried and true combination.

Kal Row

dont put all your eggs in one basket...

you already need filtering/humidification/dehumidification/ac
so you might as well put in a forced air furnace with it to back up your radiant and to bring your house to temp quickly if you turn it off for the day - and protect extremities of the house on those really cold nights as the house air temp with radiant heat is much lower and will leave the edges to the house unprotected against freezing pipes

and remember with radiant, the air in the house is still, so you need to dust more often, and when you do you need to run the forced air system to filter – and you don’t want it blowing cold air around, forced air people use that fact to sell against radiant
you already need filtering/humidification/dehumidification/ac
so you might as well put in a forced air furnace with it to back up your radiant and to bring your house to temp quickly if you turn it off for the day - and protect extremities of the house on those really cold nights as the house air temp with radiant heat is much lower and will leave the edges to the house unprotected against freezing pipes

and remember with radiant, the air in the house is still, so you need to dust more often, and when you do you need to run the forced air system to filter – and you don’t want it blowing cold air around, forced air people use that fact to sell against radiant

GMcD

Back-up systems

While I agree on the general points you raise, Kal, note that in my opinion nobody should be installing "just radiant". That's only half of a proper building system, with ventilation being a mandatory requirement anyway. My point is that the "ventilation-only" air system can be smaller than a typical "forced air" system that provides hot air and cold air for comfort control.

And the issues of "quick heat pick-up and freeze protection are valid, but if one spends the proper design attention to the building envelope and window design and selection, those potential risks and needs will be minimized. Start with the design of the building envelope first, and the remaining risks and comfort control systems are minimized. Even in New England, a proper envelope design will minimize the perceived "need" for "air conditioning (mechanical cooling) in the first place. A little bit of mass in the house design will go a long way to shave those peak loads as well.

Unknown

how are you planning to get the initial humidity differential between indoor and outdoor air in the summer such that an ERV will actually do anything to the humidity in the house in the summer?

I'm not trying to be flip, I'm keenly interested. I've been cautiously poking the radiant cooling dog with a long stick, but I have not seen anything yet that makes me think it's feasible in new england with our high humidity summers, without dedicated dehumidification elsewhere... which is practically AC in itself, so not much benefit.

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Dale

Basement?

If you have a basement that you don't mind duct work in the simple duct system like a regular wa furnace will probabably be the least cost and will work fine, you can use a cheap 80% furnace as an air handler and even have backup heat source should the boiler go down. Next favorite is a mini split, the modern ones can have separate inside units fed from one outside unit. If you need alot of cooling and don't want duct work in the basement the unico works but you will need to think about the insulating of the system in the winter.

GMcD

Couple of ways for de-humidification

Bear in mind I'm on the Left Coast, Pacific NW and don't get much of a chance to design for hot/humid climates, but here goes, using some off the cuff numbers:

First of all, design the house so that the cooling loads are less than 12-15 Btuh/SF. This will allow you to run the coldest cooling water temp at between 62-63F. Then that tells you that the maximum dewpoint allowable in the house should be not more than 60-61F. At an ambient air temp of 74F, that's equal to 40-45% RH.

Now, determine the amount of internally generated humidity loads (usually not many in summer, other than plants and people, and maybe cooking spill from the range if the range hood can't capture it all), and determine the exterior enthalpy and decide on the best approach. If you can squeeze enough moisture out of the incoming outdoor air for ventilation, to supply air at say 65F at 40%RH (dewpoint = 50F) using the primary water temperature or a separate chilled water secondary loop from the chiller unit in series with the ERV, then that will allow enough absorbent capacity in the air to pick up any internal humidity sources and exhaust them while maintaining an average dewpoint of less than 45% inside the house, given that the air change rate will be around 1 to 1.5 ACH for a good ventilation rate. In extreme climates, this may take a small split system refrigerant unit to a cold refrigerant coil in the ventilation duct to squeeze out enough moisture from the incoming outdoor air. If necessary, that air can be re-heated by the ERV, or by a series pipe loop from the return water side of the primary loop in cooling mode. Depends on the best spot to de-humidify- upstream or downstream of the ERV unit - climate specific.

Another approach could be to use a small standalone "in-house" recirculating dehumidification unit like they use in the SE climates for house dehumidification. The size of the house matters as to the best cost-effective approach - the smaller the house, then a small recirculating dehumidifier should be fine. The bigger the house, then the "engineered system" would be more cost-effective.

There is some good data as to how hard one has to drive a radiant cooling system to cause visible condensation on the radiant surface at Dr. Mumma's website - link:

http://doas-radiant.psu.edu/7-2.pdf

http://doas-radiant.psu.edu/IAQ3.pdf

http://doas-radiant.psu.edu/cond_control_fall_03.pdf

And if you scroll through the list of papers at this link:

http://doas-radiant.psu.edu/papers.html

you'll find more stuff. Basically radiant panels are a radiant surface, same as a slab, a plaster wall, or whatever- the key is keeping the supply water temp, as well as the radiant surface, above ambient dewpoint (by corollory - keep the ambient dewpoint below your desired radiant cooling operating temp).

Unknown

excellent... thanks for the thought food Geoff!

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Constantin

Thank You!

Like Rob, I'd love to learn more about this technology. It's too late for the house I live in now (as cooling the place with floor radiant is unlikley to work well) but all that info will be food for thought for a while!

DaveGateway

Keep it simple

Like you said, if you're only cooling for 2 months and heating for 7, why bother with such a big AC invetment?
I'm sure some of the multi-evaporator ductless mini-split systems would be the best. Id you don't like the wall mounted evaporators, they now have units that can suspent in the ceiling over a hallway where the unit would pull return air through a ceiling grill and then pump cold air out several small unico like flex ducts to multiple rooms. Why bother with a large duct split system in a house? It only allows more cold air into the structure durring the winter.

Weezbo

You'd be suprised.

do i want it in my home? maybe not. Perhaps when i retire ,i will put a home together with a hrv with a hepa filter and uv lights for IAQ IEQ and radiant cooling(space conditioning)and radiant heat with it all very well balanced....and as few products that out gas as possible, mostly to improve the entire living area i will have a ventilation system that runs into a central glass walled and ceilinged garden. i would rather build a smaller home on all one level with less energy use and that improve my environment and slow the loss of energy down ...than a larger home of multiple levels with all kinds of bells an dodads that i really dont need and wont be easy to remember what needs fixing and maintaining next and would probably stress me out trying to get the phone number of someone who still knows how to do that sorta work. I vote keep it simple,spend the dollar for systems that intergrate and function well together and dont affect my health adversely..

GMcD

Healthy systems

Well, in that case the simplest system is a geothermal heat pump with some wind power for the electricity. Mass burning of fossil fuels for scorched air (and thermal electrical plants) is probably the biggest impact on your health. Nobody seems to want to put a cost to the environmental impact as part of the building costs.

Remember - human comfort is 50% radiation, 30% convection and 20% perspiration. Radiant heating and radiant cooling with some air motion (ventilation) conditioned to the right humidity is 100% human comfort.

See these links:

http://www.eccacoil.com/main-end-uses/buildings/document.asp?Ref=42&RefTop=57

http://www.squ1.com/index.php?http://www.squ1.com/passive/passive.html

Cheers from the extremely Wet Coast

jim_49

You never mentitoned if this home is your primary living home or a weekend home.If it is a 2 nd. home, I would advise you stay away from RADIANT or HOT WATER HEATING. Your going to need antifreeze inthe system which can be very expensive.Every 3-5 yrs $2000. Also it will take your home 8-12 hrs to heat up if you turn your t-stat down 20 degrees. A gas or oiled fired furnace, or boiler-fan-coil with A/C attached would be a better choice. My choice would be a furnace with a/c coil becauce there is no water in the system to freeze.

Scott Miller

relief and temperature valve

What pound pressure and temperature valve should be used on a dyna-therm summer winter hook up where the cold water feeds the water tank for hot water?

Ted_9

I'm sorry but do not fool yourself into thinking that because we live in New England, we only need a/c for a month or so. Humidity removal is needed for the entire summer. Stop convincing yourself that its not worth the purchase.

PATRIOT HEATING & COOLING, INC.

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Gary

OFF PEAK HEAT STORAGE

THIS UNIT STORES HEAT AT OFF-PEAK RATE AND CAN BE USED FOR RADIANT OR FORCED AIR . THIS UNIT DOES RADIANT , FORCED AIR AND AIR CONDITIONING.

Jim_19

Primary

This will be our primary home. But like most of us in New England, I hope to be eventually able to spend some amount of time in the warm sunny south during the dead of wintah!

I understand that a radiant system would need antifreeze - just in case. $2,000. seems a little high. How often do you have to replace the stuff?

I won't consider any hot air solution. Been there, done that. From what I've heard and seen so far, something on the order of the Unico system mentioned above seems perfect. I need to collect a lot more information to see if the economics work for us.

Already learned a lot! Thanks.

Constantin

I disagree with the need for glycol in 2nd homes...

... I have been to several secondary homes with radiant heating systems. None of them use glycol. Instead, the owners set their heating system back to 55°F when they leave and have an central alarm if the heating system can't fire or the temp drops below 50°F. That gives a local heating pro some time to get over there and fix the situation before it gets critical.

One home that I recently spoke about here on the Wall has two Buderus G124X's running in the basement. You'd think that having two boilers that are equally capable of keeping the house warm would bring a measure of redundancy. Not so. Both failed within hours of each other due to faulty flame sensors (on LP!). The owner learned the hard way about ice storms, now she has a genset to provide emergency power to the heating system.

Besides, a big benefit of keeping the house to temp is that you don't have to worry about draining the potable water system, no need for glycol in all the P-traps, toilet bowls, etc. and best of all, the heating system has just water in it, the lowest cost HX transfer medium with the highest efficiency. IMHO, reducing the life of pumps, efficiency of the HX medium, etc. is only acceptable when there are no other alternatives.

Uni R

I'll second that...

Radiant, an ERV if the home is tight and a split ductless A/C system.

Unknown

I strongly disagree. We do vacation homes all the time with high and low mass radiant systems.

A freeze alarm with phone switch provides plenty of cheap protection and allows the user to trigger occupied heating temperatures remotely. Works great!

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Bob Morrison_3

Remarks on residential HVAC approaches (BM)

Adding chilled water radiant to an existing heating hot water radiant distribution system is attractive until the cost is considered. The costs of a small chiller and controls is too high relative to the traditional (DX coil) approach.

A good approach is the following:

1. above all, build very tightly (low ACH) and thermally efficient: your first costs of all HVAC systems will be much less than typical new construction.
2. Install heat recovery ventilation unit (for New England, don't bother with an ERV)
3. Heat with hot water distribution to radiant, panels or coils
4. Cool with a dedicated high-velocity, small diameter duct system, such as Unico.

This approach is cost-effective and comfortable, but, of course, so are others!

Bob

GMcD

On-going energy cost

But what is the on-going energy cost of using DX/air to provide cooling? Costs for energy are only going up, and if the house loads are minimized anyway, I argue that there is a very small premium for a small air cooled water chiller set vs DX splits, but long term operation and energy will be lower due to finer control on the chilled water, and the pipes are in the floor anyway. All this assumes a radiant SLAB style installation. Staple up and wood frame is not something I can even talk about because of the energy inefficiencies.

Bob Morrison_3

Air cooled chiller versus air cooled split system?

I believe that many DX split system condensing units will operate more efficiently than the few available, small air cooled chillers. A three ton DX condensing unit can approach 18 SEER (http://www.aceee.org/consumerguide/topcac.htm). I don't know any small chillers that are even close to that performance. For example, the Multiaqua is in the range of 10 - 12 EER. http://www.multiaqua.com/pdf/chiller.pdf. Do you know of others that are better?

The problem is that there are very few choices in micro-chillers and they're not subject to model building codes standards for performance.

Don't get me wrong: I applaud your creativity and discussion of a cool radiant alternative. I simply do not believe that the alternative is practical with today's choices.

Bob

Constantin

There are more choices...

... for example, one doesn't have to limit oneself to air based systems. For example, the COP of most ground-source heat pumps blow the doors off of all but the most efficient air-based competition, particularly in very hot, humid climates where the performance of an outdoor condenser will drop when its needed most, while a properly-sized GSHP will truck along quite nicely, and provide free hot water and/or pool heating all summer to boot.

When the floor or the ceiling are used as a heat absorber (i.e. in chilling mode), the huge surface area will work to your advantage - the solution doesn't have to be as cold as it would if it was running through an air handler, the same way that a fan-coil usually requires a lot hotter water than a radiant system to keep a room warm. This translates into energy savings and the ability to modulate the water temp gives you very fine temp control in any space w/o resorting to VS air handlers.

Naturally, no ceiling radiant cooling system will show up in the ARI catalogs because all of them are "custom" by nature - no two rooms are alike. Thus, getting an exact bead on the SEER rating of a chilled water radiant cooling system is a moving target at best. However, based on EU research that you can marvel at over at naturalcooling.com (who happen to make ceiling radiant systems, apply grain of salt here), the overall effiency of a radiant ceiling is 30% higher than that of a comparable an air-based system.

Lest we forget, for a super-high-efficiency, properly-sized AC system to work, you need ducts, ducts, and more ducts. Going Unico or Spacepak is not an option, as neither system has a high efficiency rating. A radiant-cooling with a minimum of ducting to provide IAQ and to remove latent heat not only increases the amount of living space inside the thermal envelope of the home, but maximizes efficiency as well.

I agree that micro-chillers (DX or H₂O) are a last resort solution, as I find them repulsive to look at, they're inefficient, etc. I would have seriously considered a ECR DX system with Karo ceiling-based radiant heating and cooling if I could have found a installer with experience and if the ECR rep had not blown me off. Striking out on both counts made me resort to RFH and two split AC systems.

GMcD

Points noted.

Yes, that's a problem for most small house sized systems. Ideally, as Constantin has alluded to, a water/water or air/water heat pump unit would be a good choice. I'm used to doing large scale radiant cooling applications, and with radiant slab cooling systems, all one needs is a closed circuit cooling tower which runs at cool nightime temperatures (in the right climate zones) to generate the 63-64F water for radiant cooling. New England could be a challenge to use a night-cooling evap cooler unit, and a very good model and set of calculations would be needed to see if there is enough thermal mass in the system to allow the 6-8 hour load offset to after midnight to allow a night cooler to work for a slab cooling system.

jerry scharf_2

keep the interior moisture down.

Tom,

Without some kind of moisture removal, dropping the interior air temp raises the humidity and puts the house at risk for serious health problems. I just don't see an ERV as being able to get the interior humidity down below 50%, which IMO is about the safe upper limit for a tight house.

Split units usually are really good at doing the moisture removal, so cooling the air makes sense to me. One of the best moisture removal units also happens to be about the most efficient condensers out there. Freus has a condenser unit with 18 EER (not the less meaningful SEER) and it looks like our system will pencil in at just over 15 EER for the whole system. Don't be confused between EER and SEER, an 18 EER is something close to 22 SEER. It also is designed to run with a fully flooded evap coil, so it's moisture removal is among the best.

The cost is an entire second transport system to handle the air. We needed this anyway to filter the air in the house several times per hour, so the split system was a no brainer.

For those folks who say don't need an ERV in the notheast, what's 90+% total energy recovery worth compared to a HRV. Also, there's no condensate to handle.

jerry

jerry scharf_2

keep the interior moisture down.

Tom,

Without some kind of moisture removal, dropping the interior air temp raises the humidity and puts the house at risk for serious health problems. I just don't see an ERV as being able to get the interior humidity down below 50%, which IMO is about the safe upper limit for a tight house.

Split units usually are really good at doing the moisture removal, so cooling the air makes sense to me. One of the best moisture removal units also happens to be about the most efficient condensers out there. Freus has a condenser unit with 18 EER (not the less meaningful SEER) and it looks like our system will pencil in at just over 15 EER for the whole system. Don't be confused between EER and SEER, an 18 EER is something close to 22 SEER. It also is designed to run with a fully flooded evap coil, so it's moisture removal is among the best.

The cost is an entire second transport system to handle the air. We needed this anyway to filter the air in the house several times per hour, so the split system was a no brainer.

For those folks who say don't need an ERV in the notheast, what's 90+% total energy recovery worth compared to a HRV. Also, there's no condensate to handle.

jerry

Brent_2

my 2 cents

About how many square feet are you looking at? I would install a higher seer dx system with the ductwork in the basement. You could have floor registers and high sidewall returns. All the ductwork would be in the conditioned space.
I can't see how you can even begin to justify an exotic radiant cooling system in your situation. You won't use it enough to put a dent in the extra cost. A properly installed dx system will be very comfortable.
I am not even sure if you can justify an unico system especially since it is new construction.
Also, since you might spend extended time away from home in the winter time I would install a strip of electric heat in the air handler. This would only be used for emergencies. You could set the HW heat zones at 45° and the electric heat at 40°. If the boiler failed, the electric heat would keep the house from freezing. The extra installation cost would be very minimal.

brent