Simplified Radiant Cooling

john_james

I have been thinking about simplifying radiant cooling controllers. Does this idea make sense? Has it already been done?

Target: retrofit or new build in smaller houses, apartments or zoned houses, specifically colder climates like Michigan, Vermont, Canada, etc. (lower dew point)

Idea: Have a fixed chilled water temperature (for example 66F/19C). Design a radiant ceiling, floor, panel, etc system to handle the sensible load at that chilled water temperature. Build a thermostat which calls for heat in the standard way, but only calls for cold when cooling is required AND the dew point of the radiant surfaces are above the chilled water temperature; lets call it a ThermoDewStat. The ThermoDewStat would have a connection for external sensors for measuring dew point.

A separate system for dehumidification would be required. A single unit per floor in a house or per apartment would probably suffice. This could keep the space around 50% RH regardless of cooling demand. The dehumidifier would probably would not even need ducting in most spaces, especially if it is centrally located.

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EXAMPLE: **A small apartment (apt.) setup would look like:**
DISTRIBUTION
(shared chilled water source) -> shared buffer tank -> shared header/manifold -> apt.'s zone valve or circulator -> ~3/4" or 1" insulated pex pipe -> apt.'s manifold -> (apt's radiant emitters)

CONTROL
ThermoDewStat and multiple dew point sensors, wired to zone valve/circulator.
Heat pump/chiller runs off buffer tank temperature.

DEHUMIDIFICATION
A single stand-alone dehumidifier in a central location with continuous drainage.

OPEN DOOR/WINDOW CONDITION
If a tenant opened a door/window and humid air caused the radiant surface to drop below dew point, all chilled water would stop flowing to the apartment. Once the door/window was closed and the dehumidifier ran to bring the humidity down and radiant surface above the dew point, the chilled water could flow again. This would not affect other apartments.
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EXAMPLE: **Retrofit: House with existing heat pump and radiant ceiling, but no cooling or ducting. Two zones controlled by thermostat + zone valve**
SOLUTION
Ensure radiant emitter is correctly sized. Replace thermostats with ThermoDewStat. Add sensors to radiant surfaces. Add supplemental dehumidification, such as stand alone units in a central location near power and install condensate drain. Enable chilled water on heat pump. Done.

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How viable or useful is this?
If it seems like a worthwhile idea I'll build a prototype ThermoDewStat

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APPENDIX

Dewpoint cumulative hours June + July + August 2022 (Eastern Ontario)
0C = 4 hours
1C = 3 hours
2C = 12 hours
3C = 13 hours
4C = 16 hours
5C = 11 hours
6C = 24 hours
7C = 40 hours
8C = 57 hours
9C = 105 hours
10C = 121 hours
11C = 144 hours
12C = 165 hours
13C = 182 hours
14C = 208 hours
15C = 163 hours
16C = 173 hours
17C = 158 hours
18C = 136 hours
19C = 167 hours
20C = 137 hours
21C = 88 hours
22C = 55 hours
23C = 25 hours
24C = 1 hours

Larry Weingarten

H @john_james , You have an interesting idea! The question to me is whether it's marketable. Can it be explained simply enough so people "get it" quickly and light up because the idea makes so much sense? Maybe with the threat of no refrigerant, as @unclejohn brought up, a water based cooling system could get some traction, but then how would the water be cooled? Maybe night time cooling via solar collectors?

Yours, Larry

clammy

Sounds dandy and extremely expensive . I feel no matter what this type of system will require a aux system to lower humidity as for chilled water a electric or gas fired absorption unit would be fine . I think being indoor space these days is limited to a shoe box for mechanicals including a buffer tank ,pumps ,3 ways valve to exactly control water and home humidity levels to determine indoor latent cooling temp while using indoor coils to lower humidity to prevent floor or ceiling condensation . It s a great idea but the practicality and cost I feel would be impractical . I have seen one system which used geo thermal and some 3 ways and a set point controller for the latent end and the rest went to unico air handlers and the mechanical room was a nightmare even though everything was insulated there was thermal migration and sweating pipes due to the system being a simple 2 pipe system using the same pipes for heating and cooling so there is no running the two at once but the boiler also made domestic hot water and the 2 way isolation valves still did not totally prevent thermal migration . This was all quite quite expensive and if it was not for a really huge rebates form the state and fed it would not have never been done . The Hvac end I believe was over 250 k and the rebate was about 1/3 . I guess the 1/3 us tax payers payed and I can say these people could have easily paid for the whole deal out of there pockets but they took our money to offset there mansions kitchen and wine cellar .
I feel the high cost of even radiant would never be considered in hud or low income housing just ain’t gonna happen plus cooling in northern climates a c is not required for a cert of occupation just heating .the other end is cost the cost would be double of a air based system and take up even more indoor room . Insulation and prevention of condensate forming on piping is a tough one especially w every one fearful of mold issues from moisture on building materials . Everyone will say of just insulate well if provisions and thought where going on while piping enough room would be left to properly insulate the piping but this insulation isn’t the piping guys issues so some times pipes do not get insulated properly due to spacing and piping yet another thing to consider . Another thought is in today world everyone wants instant everything .if your waiting for it to get cool w a radiant cooling you will be waiting like radiant heating it’s not fast and w a radiant cooling there will be no set backs due to the time it takes to cool the space . Trying not to be negative about your idea but cost is what keeps hydronic and radiant systems out of most new homes maybe hydro air or baseboard but hardly any mid tp low temp system w all radiant and or panel rads . Even when it is all radiant there’s usually a lot of corner cutting other wise the contractor would go broke and leave penniless .When taking w builders or gc there usually want the cheapest being they won’t be living there or paying the utility bills .
Peace and good luck clammy

john_james

Larry Weingarten said:

H @john_james , You have an interesting idea! The question to me is whether it's marketable. Can it be explained simply enough so people "get it" quickly and light up because the idea makes so much sense? Maybe with the threat of no refrigerant, as @unclejohn brought up, a water based cooling system could get some traction, but then how would the water be cooled? Maybe night time cooling via solar collectors?

Yours, Larry

Yeah, marketing it is probably not going to be easy. I was thinking about Air-to-water heat pumps, since they can do heating too. I've never thought about solar collectors before.

john_james

clammy said:

Sounds dandy and extremely expensive . I feel no matter what this type of system will require a aux system to lower humidity as for chilled water a electric or gas fired absorption unit would be fine . I think being indoor space these days is limited to a shoe box for mechanicals including a buffer tank ,pumps ,3 ways valve to exactly control water and home humidity levels to determine indoor latent cooling temp while using indoor coils to lower humidity to prevent floor or ceiling condensation . It s a great idea but the practicality and cost I feel would be impractical . I have seen one system which used geo thermal and some 3 ways and a set point controller for the latent end and the rest went to unico air handlers and the mechanical room was a nightmare even though everything was insulated there was thermal migration and sweating pipes due to the system being a simple 2 pipe system using the same pipes for heating and cooling so there is no running the two at once but the boiler also made domestic hot water and the 2 way isolation valves still did not totally prevent thermal migration . This was all quite quite expensive and if it was not for a really huge rebates form the state and fed it would not have never been done . The Hvac end I believe was over 250 k and the rebate was about 1/3 . I guess the 1/3 us tax payers payed and I can say these people could have easily paid for the whole deal out of there pockets but they took our money to offset there mansions kitchen and wine cellar .
I feel the high cost of even radiant would never be considered in hud or low income housing just ain’t gonna happen plus cooling in northern climates a c is not required for a cert of occupation just heating .the other end is cost the cost would be double of a air based system and take up even more indoor room . Insulation and prevention of condensate forming on piping is a tough one especially w every one fearful of mold issues from moisture on building materials . Everyone will say of just insulate well if provisions and thought where going on while piping enough room would be left to properly insulate the piping but this insulation isn’t the piping guys issues so some times pipes do not get insulated properly due to spacing and piping yet another thing to consider . Another thought is in today world everyone wants instant everything .if your waiting for it to get cool w a radiant cooling you will be waiting like radiant heating it’s not fast and w a radiant cooling there will be no set backs due to the time it takes to cool the space . Trying not to be negative about your idea but cost is what keeps hydronic and radiant systems out of most new homes maybe hydro air or baseboard but hardly any mid tp low temp system w all radiant and or panel rads . Even when it is all radiant there’s usually a lot of corner cutting other wise the contractor would go broke and leave penniless .When taking w builders or gc there usually want the cheapest being they won’t be living there or paying the utility bills .
Peace and good luck clammy

Thanks for your honesty.

Yeah cost might be too much. The rebates make me laugh. I worry most government environmentalism has become about subsidizing companies and the wealthy.

My thought for dehumidification is a single portable dehumidifier on each level of a house / each apartment. Set it up for continuous drainage behind some louvered doors in a small closet, probably put the manifold for the radiant pipes there too. Something like a 20 pint unit uses 241 watts and is about $200 + PEX pipe for condensate drain. Easy to replace if it fails. The downside is the added heat. The upside is the whole system only requires 66F water to cool and can dehumidify in the fall and early spring, when no cooling is needed.

I was thinking retrofitting a single monobloc air to water heat pump and buffer tank shared amongst a small rental property with 3-6 units. No ducts, except if ventilation is required. The radiant ceiling would be good for heating and cooling and enable lower water temperatures.

Fan coils are cheaper. Probably the way to go in retrofits. My family has a similar building to what I've described above and it's been on my mind for a few months now. I'll have to do the math.

Talking this out shows me how niche of a product this would be. Probably only makes sense in retrofits of apartment buildings, with owners who care about very long term operating costs and comfort. A small market indeed.

I'll probably still build the ThermoDewStat. Should be $100 and a couple weekends of tinkering.

hot_rod

I see a need for a control like this as a2whp become more popular. Quite a few variations in Germany where radiant cooling panels are more common.
Rehau has done a handful of large radiant ceiling jobs, I suspect the building automation watches dew point somehow. There were a few radiant panel products at AHR for radiant cooling ceiling installations

Taco has chilled beams at their building in a humid RI climate, maybe they will share the control used.

Head over to the ISH show in Frankfurt next week, I’ll bet you would see many controls like you are considering.🧐

Joe Mattiello

Thanks for pointing out Taco's Innovation Development Center, (TACO learning Center) does enjoy Chill beam technology. I asked our Controls Expert Tom to share some knowledge on controls taco uses.

In the Taco Learning center we use the iWorX CHB controller (Chilled Beam Controller). Our Clarity product line also has a Chilled Beam Application written for the controllers. The key points of the control are knowing what the supply dew point is from the DOAS unit and also the dew point of the space. The heating loop is activated when required and the cooling loop only activated when the dew point will not allow condensation on the beam.

It is our belief, in a residential system this solution would be very costly for several reason.
• There would need to be a temp and humidity sensor in each space
• There would need to be a sensor on each window and door to indicate when it is open
• Chilled and hot water are needed for the chilled ceiling loops
hopefully this was helpful:)

dko

The Taco System M webinar I watched comes to mind.
I believe it's the first plumber recognizable brand to come in the market with the Air to Water heat pump.
Also "plumber friendly."

Never found out the cost of the unit.. hopefully very competitive to boost it's acceptance.

Tim_D

Taco iWorx did all of this with their CHB controller so the sequence of operation already exists and is well tested. Just needs to be put into a new platform.

archibald tuttle

my issue with radiant cooling is what mass are you circulating the cool water through that would be able to sustain the changes in humidity without condensing. i would then it would be the opposite of thinking about radiant heat where the idea is to have a lot of mass and dewpoint is not an issue (cf. say shoulder season when our indoor temps run warm because even ODR is not enough to allow the mass to cool down without overheating the house.

so really you are talking about a cooling system where virtually all the mass is the water. i guess that is conceivable but it can't double as a heating system without sacrificing some of the background comfort of radiant mass heat.

clammy

What’s the point of doing a radiant cooling when you are only going to lower the sensible very little not the latent and will need secondary system .what in each room you put a dehumidifier sounds half witted. Not to bust but didn’t you just have issue w a simple thermostat now your gonna self design a radiant cooling system really ? You can laugh at rebates but unless you can prove and get a ahr listing Amdahl rating there will be no rebate . The over all price of just a real radiant system not a fantasy radiant system is usually out of reach for most u less it’s being installed for free . Case history , I help a fellow contractor out years ago he loved to do what I call ego gratifying jobs yeah geo therm ,radiant ,vissemann boiler unico s hi v systems every where the job was in the 200 k range . At the end he just about paided his guys and walked away w his shirt on but his ego and we can do anything ego left a smile on his face but didn’t pay his bills including some equiptment and supplies . i Know it’s possible but it cost prohibitive unless as the above case you get a huge rebate to knock the over all cost down like 1/3 . But here’s the real issue if you have the bucks for say radiant heating and cooling to be installed in your new Mc mansion well I personally feel that you got the bucks to fork over your own money to do so . It’s total bull to give a rebate to some one who’s building a 5 mil house they should get nothing they already have the money and will get a rebate to offset a 120 k kitchen .
Get real ,your Fantasy system will never be installed in any low income house nor will the 120 k kitchen . Not to bust but in if it where so easy and so workable and so great I think people much smarter then us would and done it already .
As I was told and may be it was just me . You are not special your just like everybody else your no smarter or stupider or no better then hence which you can . I know in today society every bodies special and every bodies a genius every body gets a pass . Well as I see it all the special people and all the geniuses that there are really hasn’t done much to improve the the distance between the haves and the have nots not those that work and those who get hand outs . Every product should be able to stand it own and not need funding through our taxes to keep afloat in which case it not a business it’s just a money burden to the tax payers .
Closing notes , cooling is a luxury people lived without for ions . If your gonna do some thing why not prove your so smart and help man kind not build a system which wil be over the cost of 99% of any one looking at a new home unless you gonna cater to the 1% who have the money but remember those 1% got there by getting the 99% to help pay for it . Personally I like working for the 99% screw the 1% nobodies make money off them that’s why there rich .
Best of luck w your already been done empty pocket system . It would be great for the getting out of the business crew being afterwards w no money that what they will be . Just one though to add being every body or just about every body knows radiant system takes hours to heat a home to set point so drastic temp set back and comfort don’t always work .i could only image how long it would take to bring a radiant cooling system without secondary cooling to reach set point . I know it would not be a 1 hour 2 degree gratification and we all know rich folks don’t like to sweat this is why they have people do there dirty work .
Wish you and your system luck ,you should install in your own home and work out all the bugs and let us know how it turns out and the cost Analysis and operational cost . Andirons the cost compared to comfort where worth it also all on the cuff no rebates let us know how it works out . Good luck clammy
Firmly based in reality not in negativity
None of this is meant to offend or insult anyone just a door bell ringing that’s it

john_james

Thanks everyone, cool to see Taco represented. I wanted to jot down some more thoughts and math, specifically with regards to my area in Canada. I should have mentioned in the original post that I am mainly thinking about air-to-water heat pumps and this is mainly an intellectual exercise rather than a commercial ambition. I am not in HVAC, I just find hydronics and heat pumps interesting, especially radiant cooling.

Also let's leave public housing and mansions out of this; focus on middle class / median housing and especially retrofits of buildings with existing hydronics. Thanks. Any thoughts or criticism about these ideas, not criticism about me personally, is welcome.

SENSIBLE COOLING

In most of Canada the sensible load comes almost entirely from the sun and interior loads; the 99% cooling temps are barely above room temperature. If a house has a reasonable glass-to-wall ratio or passive solar overhangs the sensible cooling load is a fraction of the heating load. A cooling load at a third of the heating load is reasonable for residences. An existing radiant ceiling or even floor designed to handle our cold winters, can easily handle the sensible cooling load.

Healthy heating gives 12Btu/h/sqft cooling for radiant floors at 66F, and 28Btu/h/sqft heating for radiant floors at 84F. That is a 42%; above the rough target of 1/3. 68F gives the 1/3 target.

Radiant ceiling can give 10.6Btu/h/sqft at 76F room and 70F water (q=1.48*(Tr-Tc)^1.1) (equation from Idronics), and 15Btu/h/sqft for heating. 70F water is above outdoor dewpoint for all but 81 hours a year. 72F gives 6.8Btu/h/sqft. That is 45% of the heating at 72F, which is above outdoor dewpoint for all but 26 hours a year. Really low dT should be able to handle sensible cooling in Canada, especially in radiant ceilings.

RISK OF CONDENSATION

Obviously external dehumidification is required, but I believe the risk of condensation with radiant ceilings is limited in time. Debunking Myths of Active Chilled Beams: What You Thought You Knew But Were Wrong, Part 1 shows it took over an hour for any water to form on a chilled beam running nearly 2F below the dewpoint. In the case of a 72F water, that means a dewpoint of 74F would probably only cause damage after 1 hour. Fittingly, a the dewpoint above 74F only happens for about an hour a year in my area of Canada.

For 70F water, that gives on 26 hours a year with dewpoint above 72F. Even if the dewpoint controllers to a system with radiant ceilings running at 70F failed horribly with windows left open, the probability of condensation occuring is low. This is all theoretical of course. What affect a radiant ceiling has vs chilled beams obviously would need testing.

For radiant floors the required low temperatures (higher deltaT) make the concerns of condensation greater.

SENSOR COST

So in a retrofit situation where radiant floor, ceilings, etc exist and are zoned, we are talking about swapping out a thermostat and adding sensors similar to this:

https://www.adafruit.com/product/5181 

They're $8 each. Maybe $25 retail to make a commercial version with nice wire connectors. Wire them to the "ThermoDewStat" with whatever cheap wire and cheap labour you want, its 3.3V and 3.2mW of power. Low voltage wire ~$1/foot. High accuracy sensors are not needed; an error of 1% RH is ~ 0.2F dewpoint.

Taking the first derivative of the sensor readings could help speed up reactions to events like open windows. Call T_crit = chilled water dewpoint + 3F. Essentially you would want to turn off the call for cooling if you saw a change in interior dewpoint that was likely to drop below T_crit, rather than just waiting for T_crit to be crossed.

@Joe Mattiello thanks for your input. I am concerned about cost too. Assuming air-to-water heat pumps could bring the source cost down (big if), that leaves the concerns about sensor cost (mainly installation cost in retrofits). Have you ever done tests in a residential setting, whether a single sensor in a room could protect a radiant ceiling or similar from condensation, specifically in climates with higher dewpoints and higher chilled water temperatures, like Canada's major cities?

Picture a two story house: 25'x40' with a thermostat and zone per floor. If the thermostat is centrally located, the cost of the sensor + wire is under $100 a room. Say the house has 10 rooms and two "ThermoDewStats" (~$200-300/each), that gives the material cost of a retrofitting sensible radiant cooling for an existing radiant ceiling (or floor?) home at around $1500.

GRANTS

In Canada our government caps retrofit grants to $5k for owner occupied single family residential properties and none of it goes to radiant emitters or a2whp. This may be changing in the future (maybe air-source heat pumps in 2023), or I may be missing something, but that is my understanding from research. Plenty of multi-use and multi-unit buildings do not qualify. So qualifying for grants is not an option. That is why I was finding it funny that generous grants were given to those 200k systems that @clammy was talking about.

LATENT DEMAND

The latent load is probably a quarter of the sensible load in the great lakes region, likely less in the praries. I am looking for more info on this. If anyone has info on average sensible heat ratios for Northern US or Canada I would be interested. The only info I can find is https://www.engineeringtoolbox.com/shr-sensible-heat-ratio-d_700.html  which gives a sensible heat ratio of 80%-95% for residences. That seems high, but again, I do not know. The ratio of sensible/latent is a determining factor in whether such a system makes sense.

In a retrofit (in, say, Toronto or Montreal), would a centrally located and properly sized portable dehumidifer be able to dehumidify an average sized floor (say 1000sqft) with the interior doors open? Cooling at night, when doors are shut is rarely a concern.

If a single dehumidifer per floor or apartment unit could manage the latent load and a single sensor per room could this is a cost effective strategy for retrofits where a low temperature radiant system already exists. Otherwise fan coils, operating at lower chilled water temperatures, doing latent and sensible cooling are cheaper.

ELECTRICITY COST

Heat pumps are more attractive with lower electricity costs. Lower delta-T water temperatures bring cost down. A heat pump without gas furnace (maybe with electric boiler backup) brings equipment cost down. Much of Canada has lower electricy rates than the neighbouring US cities. This makes a2whp and radiant cooling more attractive than cities across the border. Time of use pricing means nightime pricing is half in Ontario, which can reduce nightime heating costs considerably.

What is happening in New York and Boston? :(

Thoughts on this idea?

Sorry for the long posts, this idea has just captured my attention.

ryanwc

For a newbie, can you define latent vs sensible load?

john_james

@ryanwc

Sensible is about temperature, like you would read on a thermostat (eg 22C).

Latent is about moisture, like you would read on a hygrometer (eg dehumidifier says 55% humidity). The energy required to phase change moist air to liquid water.

For example

• A hot desert has high sensible load, but little/no latent load.
• A damp and cool basement has high latent load, but little/no sensible load.