Thermal Mass: 3 Kinds?

gasfolk

we thought Thermal Mass might finally explain the variability in the numbers, but with differing opinions on issues like sizing, part load efficiency, buffering, and (now) thermal mass, it seems like a leap of faith in whomever we ask.

Sure, a new boiler will be more efficient, but no one can really say how well our house is functioning now to predict future savings. Makes it hard to justify replacing a functioning boiler. Anyway, at least the present boiler keeps the house comfortable.

Thanks.

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

Have found references to three kinds of Termal Mass, each with different properties depending on location: 1) in the Thermal Shell, 2) interior to the shell, and 3) part of the heat emitters (e.g. RFH).

References suggest that 1) mass in the shell may lower heat loss by increasing “mass-enhanced” R-value; 2) mass in the interior may dampen and delay temperature changes; and 3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Anyone know of any other significant type of or location for Thermal Mass? References?

Thermal Mass and R-value: Making Sense of a Confusing Issue

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

Have found references to three kinds of Termal Mass, each with different properties depending on location:

1) in the Thermal Shell,

2) interior to the shell, and

3) part of the heat emitters (e.g. RFH).

References suggest that

1) mass in the shell may lower heat loss by increasing “mass-enhanced” R-value;

2) mass in the interior may dampen and delay temperature changes; and

3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue

Anyone know of any other type of Thermal Mass with significance for hydronic heating? References?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

Have found references to three locations for Thermal Mass:

1) in the Thermal Shell,

2) interior to the shell, and

3) part of the heat emitters (e.g. RFH).

References suggest that properties differ with location:

1) mass in the shell may lower heat loss by increasing “mass-enhanced” R-value;

2) mass in the interior may dampen and delay temperature changes; and

3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue

Anyone know of any other type of Thermal Mass with significance for hydronic heating or any other significant properties? References?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

Have found references to three locations for Thermal Mass: 1) in the Thermal Shell, 2) interior to the shell, and 3) part of the heat emitters (e.g. RFH).

References suggest properties differ with location:

1) mass in the shell may actually lower heat loss through “mass-enhanced” R-value in certain climates;

2) mass in the interior may dampen and delay temperature changes; and

3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue
Is there any other type of Thermal Mass with significance for hydronic heating or with other significant properties? References?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

References suggest three locations for Thermal Mass: 1) in the Thermal Shell, 2) interior to the shell, and 3) part of the heat emitters (e.g. RFH).

References also suggest properties differ with location:

1) mass in the shell may actually lower heat loss through “mass-enhanced” R-value in certain climates;

2) mass in the interior may dampen and delay temperature changes; and

3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue.

Is there any other type of Thermal Mass with significance for hydronic heating or with other significant properties? References?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

References suggest three locations for Thermal Mass: 1) in the Thermal Shell, 2) interior to the shell, and 3) as part of the heat emitters (e.g. RFH).

Sane references suggest properties differ with location:

1) mass in the shell may actually lower heat loss in certain climates through “mass-enhanced” R-value of the shell;

2) mass in the interior may dampen and delay temperature changes; and

3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue.

Is there any other type of Thermal Mass with significance for hydronic heating or with other significant properties? References?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

References suggest three locations for Thermal Mass: 1) in the Thermal Shell, 2) interior to the shell, and 3) as part of the heat emitters (e.g. RFH).

Same references suggest properties differ with location:

1) mass in the shell may actually lower heat loss in certain climates through “mass-enhanced” R-value of the shell;

2) mass in the interior may dampen and delay temperature changes; and

3) mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue.

Is there any other type of Thermal Mass with significance for hydronic heating or with other significant properties? References?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

References suggest three locations for Thermal Mass: 1) in the Thermal Shell, 2) interior to the shell, and 3) as part of the heat emitters (e.g. RFH).

Same references suggest properties differ with location:

1) Mass in the shell may actually lower heat loss in certain climates through “mass-enhanced” R-value of the shell;

2) Mass in the interior may dampen and delay temperature changes; and

3) Mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue.

Is there any other type/location of Thermal Mass with significance for hydronic heating or with other significant properties? Any references?

Thanks,

gf

Boilerpro_5

Any other subtypes of Thermal Mass?

References suggest three locations for Thermal Mass: 1) in the Thermal Shell, 2) interior to the shell, and 3) as part of the heat emitters (e.g. RFH).

Same references suggest properties differ with location:

1) Mass in the shell may actually lower heat loss in certain climates through “mass-enhanced” R-value of the shell;

2) Mass in the interior may dampen and delay temperature changes; and

3) Mass in the heat emitters may cause lag in responding to temperature changes, resulting in over or under-heating.

Thermal Mass and R-value: Making Sense of a Confusing Issue.

QUESTIONS: Is there any other type/location of Thermal Mass with significance for hydronic heating or with other significant properties? Any references?

Thanks,

gf

Boilerpro_5

For my modeling career...

In a model of heat flow, perhaps four types of Thermal Mass to consider??

Type 1 (Berm): External mass in contact with the shell (e.g. earthen berms, soil below and around the foundation--perhaps negligible only in a house on stilts).

Type 2 (Shell): Mass in the thin shell of the thermal boundary (always good, but hard to measure?).

Type 3a (Internal, Structural): Mass of interior structural components (excluding heat emitters).

Type 3b (Internal, Moveable): Mass of furniture and possessions (perhaps often negligible?).

Type 3c (Internal, Emitting): Mass of the heating system (sometimes good sometimes bad?).

Would welcome any comments, criticisms, or suggestions.

Thanks,

gf

Unknown

I would put forth that the relevance of mass for heating system design is pretty small, other than for control issues when your emitter is the mass which must be controlled. If the mass is elsewhere, then the load presented to your emitter will be fairly consistent and not a major controls issue.

I generally acknowledge to my clients that the mass effect will have an effect on overall energy usage, however I cannot design a system using a "mass enhanced R value" in MOST climates. The reason being if they see a consistent cold snap, and it's cloudy, their mass is not helping them, and I still need to keep them warm.

But I would say that such situations are very good arguements for modulating burners or staged heating, because the system will be oversized for most situations, moreso than in a low mass home.

Just my two cents..

Boilerpro_5

Thanks Rob. Succinct and well put.

Anyone else?

gf

bob_46

GF

you mention earth berms. I had one customer with an earth bermed house, in fact about 80 to 90% underground including the roof. The house is located in CO. It was designed by some famous architect on the east coast and the mechanical system was designed by a mechanical eng. firm on the east coast. No insulation. It cost a fortune to heat. The owner had gigabucks and bitched about the heating bill. The interesting thing is that the house was empty from the end of Oct. to the end of april and during that time the boilers were turned OFF and the house never went below 55F. I serviced the house for 10 yrs. and got to watch the same senario each year. Motha earth is one hell of a heat sink.

jp_2

drop #1

external mass will only show up as outside T, so either you have a mild climate or a berm.

but remember, ground temps are not constant near surface.

jp_2

more explaination?

which numbers are you talking about?

"""...but no one can really say how well our house is functioning now to predict future savings.""""

well gf, the only way to accuarately predict future saving is to 'measured' heatloss . the greatest software on earth is just an educated guess.

I do not see it as that hard to measure your actual heatloss. two thermometers and a flow meter for a boiler.

Mike T., Swampeast MO

I feel your frustration and pain gf...

Have been in that exact situation where the present boiler keeps the place comfortable and would probably live for decades with little maintenance.

I endured EXTREME ridicule for replacing it with the most expensive boiler on the market but such has drastically reduced consumption.

The only "leap of faith" I've ever suggested to you is to put TRVs on ALL of your radiators, add simple mechanical reset and forget about condensation problems. (Just use a differential pressure bypass valve and "dial in" some bypass by ear...) If condensation problems occur with your iron rads, gravity piping and extremely oversized traditional boiler it would be the great exception.

Such could only improve comfort and would likely give modest fuel savings. Then observe the firing of the boiler and the temperature of the rads over a few years and you'll understand just how much fuel you can save with a directly connected condensing/modulating boiler.

gasfolk

Hi JP and Mike,

Instead of adding a buffer tank, could a variable-differential thermostat eliminate short-cycling by allowing the entire thermal mass of a house act as a buffer? Instead of a steady 68F, let the indoor temp fluctuate a few degrees, say from 67 to 69? Markedly improved boiler efficiency with no change in mean indoor temp--and accessible to every over-sized boiler for the cost of a variable-differential thermostat (Robertshaw?)?