Heat and Vent

Heat and Vent — Fifty Under (content sections)

A plain-language primer

Why keeping a greenhouse or a barn dry costs so much — and what a ground-source heat pump does about it.

For growers, livestock producers, and their partners

01 · The problem, plainly stated

You pay for the heat. Then you throw it away.

You heat the building. Then your plants transpire, or your animals breathe and urinate, and the air inside gets wet. Wet air means condensation on the glass and the steel, mold and disease pressure in the crop, frozen ceilings, wet bedding, and a barn that smells wrong.

The only tool most operations have to get rid of that moisture is to open the vents or run the fans. Which means throwing out the air you just paid to heat, and pulling in cold outside air that you now have to heat all over again.

You pay twice. Once for the heat, and once for the heat you deliberately threw away to keep the building dry.

The heat-and-vent trap

There is no setting on that dial that is actually comfortable.

Every operator knows the squeeze. Seal the building up tight to hold the heat, and the humidity climbs until the crop or the herd suffers. Open it up to protect the crop or the herd, and you watch your fuel go out the ridge. There is no setting on that dial that is actually comfortable — and the better insulated and tighter your building is, the sharper the trade-off gets.

02 · The hidden second half

Burning fuel makes it worse

When you burn propane or natural gas, water vapor is one of the products of combustion. An unvented heater is quietly adding moisture to the very building it is being run to keep warm — which means it is adding to the humidity problem that forces you to vent in the first place.

So the fuel bill has a hidden second half. You are paying for heat, and you are paying to remove the moisture your heat source created.

03 · The alternative

What a ground-source heat pump does differently

A ground-source heat pump doesn’t burn anything. It moves heat between your building and the ground beneath it, using a loop of buried pipe and electricity to do the moving. That difference in mechanism is what breaks the heat-and-vent trap, in five distinct ways.

It dries the air without opening the building

A heat pump can create a cold surface that pulls moisture out of the air as liquid water — the same way a cold glass sweats on a summer day. It then takes the heat it just captured and puts it straight back into the room, warming that same air before returning it. The moisture leaves down a drain instead of out a fan.

That is the core move: it breaks the link between drying the building and emptying it of heat.

It doesn’t create the moisture in the first place

No combustion inside the building means no water vapor produced. Your drying load gets smaller before you have done anything else.

Cheaper heat softens whatever venting is left

A good ground-source system delivers three to four units of heat for every one unit of electricity it consumes — because most of that heat is moved, not made. For the air you do still exchange, each unit of heat that goes out the vent costs you a fraction of what it used to.

It matches the way you actually want to deliver heat

Ground-source systems are at their most efficient producing warm water rather than hot water — roughly 90 to 120°F. That happens to be exactly what root-zone piping, bench heat, and in-floor hydronic systems want. Heating the plant or the animal directly, instead of heating the entire air volume, means less hot air stacked up under the roof waiting to escape — and less to lose whenever you do vent.

The same loop runs backward in summer

Greenhouses vent enormously in warm weather just to shed heat, and heat-stressed dairy cows and sows give up production. The same buried loop that warms you in January takes heat out of the building in July and parks it underground — where some of it is still there, waiting, when the weather turns. The summer half of the problem becomes a winter asset.

Two ways to dry the same building

Illustrative of the mechanism described above, not a system drawing.

3–4 : 1

Units of heat delivered per unit of electricity consumed by a good ground-source system — because most of that heat is moved, not made.

90–120°F

Where ground-source systems are most efficient — and exactly what root-zone piping, bench heat, and in-floor hydronic want.

Summer → winter

Heat pulled out of the building in July is parked underground, where some of it is still waiting when the weather turns.

04 · Straight talk

What it does not do

None of this eliminates fresh air.

A barn still needs air exchange to manage ammonia, carbon dioxide, and pathogen load, and those minimums are set by animal health, not by moisture. A greenhouse still has agronomic reasons to move air.

What a ground-source system addresses is the extra ventilation stacked on top of that floor — the venting you do purely to chase humidity, which in cold weather is usually the larger share of the two. The floor stays. The penalty on top of it is what goes away.

05 · The bottom line

Why this shows up on the bottom line

The energy savings are real and they are the easiest thing to measure. But in most operations they are not the biggest number on the page.

Tighter control of temperature and humidity, held steady without swinging the building open to the weather, is a production story: better growing conditions, lower disease pressure, less heat stress, less shrink. In a greenhouse, a few percentage points of yield is usually worth more per year than the entire fuel bill it took to get there. In a barn, the same control shows up in animal comfort, air quality, and performance.

And because the heat comes from the ground and the grid instead of a delivered fuel, the cost stops moving every time something happens somewhere else in the world.

Where Fifty Under fits

These systems work, and they have worked for decades — but they have to be designed and right-sized for your specific operation, and that is genuinely specialized work. We do that part so you don’t have to: evaluating whether ground-source makes sense on your site, designing the system, managing the drillers and contractors, handling permitting, capturing the federal and state incentives, commissioning it, and looking after it once it runs.

If you would rather own the system outright — and many farms see a borefield as a fifty-year, multi-generational asset — we will help you build and own it. If you would rather not put up the capital, we can provide it and sell you the heating and cooling as a service. Either way, the engineering is the same and the conversation starts the same: is this a good fit for your site?

Start the conversation Get a report on your site

Going deeper

Check the argument against the literature

Selected published research, for readers who want to check the argument against the literature. All of it is publicly available; most is open access.

Greenhouses and controlled environment agriculture

de Zwart, H.F. Energy conserving dehumidification of greenhouses. Acta Horticulturae 1037, International Society for Horticultural Science.

States the mechanism directly: as greenhouses become better insulated and more airtight, humidity rises and growers vent to remove it. Removing the moisture internally instead prevents the loss of heat through the vents, and condensing that moisture on a cold surface recovers heat.

Chantoiseau, E., Migeon, C., Chasseriaux, G., & Bournet, P.-E. (2016). Heat-pump dehumidifier as an efficient device to prevent condensation in horticultural greenhouses. Biosystems Engineering, 142, 27–41. doi:10.1016/j.biosystemseng.2015.11.011

The clearest quantification of the gap. The heat-pump dehumidification system used several times less energy than conventional venting-and-heating, and its total operating cost came in below ventilation with a heat exchanger.

De Halleux, D., & Gauthier, L. (1998). Energy consumption due to dehumidification of greenhouses under northern latitudes. Journal of Agricultural Engineering Research.

Foundational work quantifying the penalty itself in cold-climate greenhouses — the baseline the alternatives get measured against.

Seginer, I., & Kantz, D. (1989). Night-time use of dehumidifiers in greenhouses: an analysis. Journal of Agricultural Engineering Research, 44, 141–158.

Identifies where the penalty bites hardest: well-insulated houses, strongly transpiring crops at night, and tight humidity targets. A useful test of whether your own facility is exposed.

Katsoulas, N., Sapounas, A., de Zwart, F., Dieleman, J.A., & Stanghellini, C. (2015). Reducing ventilation requirements in semi-closed greenhouses increases water use efficiency. Agricultural Water Management, 156, 90–99.

Shows what else follows once mechanical cooling and dehumidification reduce the need to ventilate — including recovery of transpired water.

Sapounas, A., Katsoulas, N., Slager, B., Bezemer, R., & Lelieveld, C. (2020). Design, control, and performance aspects of semi-closed greenhouses. Agronomy, 10(11), 1739. doi:10.3390/agronomy10111739

A good starting review of the semi-closed greenhouse concept, which attributes its energy savings principally to reduced ventilation losses.

Livestock barns

Han, Z., Wang, K., Dai, L., Li, K., & Wang, X. (2024). Recent application of heat pump systems for environmental control in livestock facilities — a review. Agriculture, 14(12), 2309. doi:10.3390/agriculture14122309

The current umbrella review of heat pumps for barn temperature and humidity control, energy efficiency, and emissions. Start here.

Sharpe, K.T., Reese, M.H., Buchanan, E.S., Tallaksen, J.E., Janni, K.A., & Johnston, L.J. (2018). Electrical and thermal energy consumption in Midwest commercial swine facilities. Applied Engineering in Agriculture, 34(5), 857–864.

University of Minnesota field measurement across commercial barns, identifying heating and ventilation as the dominant energy users. This is where the money is.

Deeken, H.F., Lengling, A., Krommweh, M.S., & Büscher, W. (2023). Improvement of piglet rearing’s energy efficiency and sustainability using air-to-air heat exchangers — a two-year case study. Energies, 16(4), 1799. doi:10.3390/en16041799

Two years of measured data putting a number on the penalty in mechanically ventilated barns: the great majority of heat loss leaves with the exhaust air.

Mun, H.S., Dilawar, M.A., Jeong, M.G., Rathnayake, D., Won, J.S., Park, K.W., Lee, S.R., Ryu, S.B., & Yang, C.J. (2020). Effect of a heating system using a ground source geothermal heat pump on production performance, energy-saving and housing environment of pigs. Animals, 10(11), 2075. doi:10.3390/ani10112075

Side-by-side barn comparison. Geothermal held temperature more effectively with no loss in animal performance, cut electricity use and cost, and roughly halved ammonia concentration — better air without more air exchange.

Licharz, H., Rösmann, P., Krommweh, M.S., Mostafa, E., & Büscher, W. (2020). Energy efficiency of a heat pump system: case study in two pig houses. Energies, 13(3), 662. doi:10.3390/en13030662

Measured rather than modeled performance in a working piglet-rearing barn and farrowing barn, and candid about where the parasitic losses are. Credible numbers.

Mun, H.-S., Dilawar, M.A., Rathnayake, D., Chung, I.-B., Kim, C.-D., Ryu, S.-B., Park, K.-W., Lee, S.-R., & Yang, C.-J. (2021). Effect of a geothermal heat pump in cooling mode on the housing environment and swine productivity traits. Applied Sciences, 11(22), 10778. doi:10.3390/app112210778

The summer half of the argument: lower internal temperature and lower temperature-humidity index than conventional ventilation-fan cooling.

Dominguez, L., & Predicala, B. (2011). Evaluation of heat exchanger, ground source heat pump and conventional heating systems. Prairie Swine Centre Annual Research Report.

North American, practitioner-facing, and blunt: over two heating seasons the ground-source system cut energy use in grow-finish rooms by roughly 45 percent against conventional forced-air heating.

Questions, or want this run against your own facility? Fifty Under LLC · david@fifty-under.com · (203) 253-3388 · fifty-under.com