Brownstone Heating System Design Analysis

Frederick Avyasa Smith

MECE E4330: Thermo-Fluids Systems Design

Prof: Dr. Sinisa Vukelic

December 18th, 2014

Table of Contents

Introduction.............................................................................................................................. 31 st and 2 nd Floor Schematics ........................................................................................................... 53 rd and 4 th Floor Schematics ........................................................................................................... 6

Analysis....................................................................................................................................... 7Heat Loads............................................................................................................................................ 7

Load Requirements Over a Year.............................................................................................................11Load Requirements Over Each Month of the Year..........................................................................11Load Requirements Over an Autumn Day..........................................................................................15

Duct Network.................................................................................................................................... 17Overview Schematic of Developed Duct Network..........................................................................19Schematics of Developed Duct Networks for Each Floor.............................................................20

Conclusion............................................................................................................................... 23

Appendix.................................................................................................................................. 25Sample Calculations....................................................................................................................... 25Code Developed for Heating Load Analysis............................................................................27

Year......................................................................................................................................................................27Month..................................................................................................................................................................31Day....................................................................................................................................................................... 37

Natural Gas Furnace Specifications..........................................................................................38

References............................................................................................................................... 47

2

IntroductionThe famous and common four story townhouses located all around the New York

City area are commonly known as Brownstones. Brownstones are townhouses that

are placed next to each other continuously to form a large row. The townhouses

share the same walls and are generally the same height. Brownstones are very old

buildings that were constructed in the mid-19th century. Buildings constructed

before the 1830s were made of brick or wood. Due to an economic boom in the mid-

19th century Brownstones started to be constructed. The growing middle class of the

time desired more sophisticated styles of housing. There were large deposits of

sandstone located in Connecticut and New Jersey. This specific type of sandstone

located in neighboring states is known as Brownstone because of its rich distinctive

reddish-brown color. The stone could be conveniently transported from these states

via barge. Thus, enormous amounts of construction using the Brownstone material

occurred. Currently, these Brownstones still exist and are very popular. However,

the heating systems used in these buildings usually are outdated and have not been

replaced in decades. New York City is a very cold place to live in the winter months.

Therefore it would be crucial for one living in a Brownstone to have an updated fully

functional heating system. Thus, a preliminary analysis on a heating system in a

classic Brownstone townhouse will take place. The analysis will take into

consideration many factors and a design of a heating system, that can operate at any

time of the year, will be devised. Heat losses through building materials including

exterior walls, windows, doors, and the roof will be analyzed in order to determine a

proper heat source for the heating system. Additionally, a piping/duct network will

be devised in order to disperse this generated heat throughout the Brownstone.

This analysis will be heavily based upon methods, calculations, and supporting

documents found in the textbook Introduction to Thermo-Fluids Systems Design by

McDonald/Magande and HVAC: handbook of heating, ventilation and air conditioning

for design and implementation by Vedavarz [1&2]. In the table below the initial

parameters for this Brownstone are summarized:

3

Table 1 Initial Parameters Regarding the Brownstone

The schematics of the four floors of the Brownstone can be found in the figures

below:

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1 st and 2 nd Floor Schematics

Figure 1 Schematic of the 1st and 2nd Floor Levels of the Brownstone Townhouse

5

3 rd and 4 th Floor Schematics

Figure 2 Schematic of the 3rd and 4th Floor Levels of the Brownstone Townhouse

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AnalysisHeat Loads

The Brownstone will be assumed to be located in the Central Park area and

additionally contain a small crawl space under the first floor. This space will have a

height of 5.66ft. For this preliminary analysis solar heat gain will not be considered.

In addition to this heat storage of the building structure and heat gain from internal

sources will not be considered. Lastly, heat loss due to infiltration will be considered

negligible due to superb insulation of the Brownstone. Overall heating requirements

will first be explored over the course of an entire year, each month of the year, and a

cold autumn day. In order to accomplish this the heat losses from the Brownstone

must be determined. The inside temperature of the Brownstone will be maintained

at 68°F for comfort. The hallways, bathrooms, and closets will not be heated for cost

saving purposes. In addition the basement area under the first floor will also not be

heated. Heat losses through the doors, walls, windows, and the roof will be found

utilizing the overall heat transfer coefficient. Most of these structures are

constructed in multiple layers. Overall thermal resistance can be represented using

electrical resistance as a model. The heat transfer rate is assumed to be constant

throughout the materials that are in series. Thus the overall heat transfer coefficient

(U-Value) can be represented as U overall=1

Rtotal. Many overall heat transfer

coefficients have been tabulated for a wide array of building materials and

configurations. These numerous tables will be utilized in this preliminary analysis. It

is noted that heat losses will be assumed to only occur from conduction in a one-

dimensional steady-state system. Thus, the equation q=UA (T i−T o )=UA∆T will be

utilized to calculate heat transfer via conduction. The equation utilizes the area of

the surface through which heat transfer is occurring and the temperature difference

between the inside surface and outside surface. In order to maintain the

Brownstone at 68°F the heat lost due to conduction must be placed back into the

Brownstone from a heat source. The Brownstone can essentially be modeled as a

rectangular prism. However not the entire surface of the prism will be analyzed

because not all of the areas are being heated. The rooms, which are to be heated, will

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have the areas that are exposed to unheated areas outside of the prism analyzed.

Heat transfer to other neighboring Brownstones and to the basement via the floor

will be deemed negligible. Because the Brownstones are enclosed between two

other Brownstones the assumption will be made that these walls in contact will

exhibit the behavior of a completely insulated region. The basement will also be

considered completely insulated by the surrounding ground, thus rendering heat

transfer negligible. For this analysis the first floor will be modeled as being

completely above ground. These assumptions will be made for simplicity in the

analysis in order to design the heating system. Again, all heat losses will be added

together to provide an overall heating load for the Brownstone. Heat loss will stem

from the roof, front, and back of the building. Overall heat transfer coefficients that

will be used for the structure of the Brownstone in this analysis can be found in the

table below:

Table 2 Overall Heat Transfer Coefficients of All Considered Structures in Preliminary Analysis

U-Values were modified to account for R-12 and R-20 insulation in the Brownstone

building materials. It is noted that brick and sandstone have similar thermal

conductivities. This table is representative of all assumptions made on building

materials and structures. In addition the doors will be assumed to be 4ft in width

and the height of the wall. Furthermore, the skylights on the top floor will be divided

between the master bathroom and two bedrooms. The figures used to determine

the U-Value for the roof, front, and back walls can be found below:

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Figure 3 Overall Heat Transfer Coefficients of Solid Masonry Walls. It is noted Construction 2 was utilized as a model. [2]

Figure 4 Overall Heat Transfer Coefficients of Flat Masonry Roofs with Built up Roofing. It is noted Construction 2 was used as a model. [2]

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The calculations that will be used for the heat loss analysis in the Brownstone can be

found in the table below. These equations utilize the U-Values that were established

and the areas of the locations that are exposed to outside conditions:

Table 3 All Developed Heat Transfer Equations that will be Utilized to Calculate Heat Losses (1)

Now that the equations for heat transfer loss have been established the heating

loads can be explored. Below one will find figures that represent loads over the

course of an entire year, month and a cold day in August. The year that was used for

analysis was 2013. This will provide the development of a system that is as current

as possible:

10

Load Requirements Over a Year

Figure 5 Overall Load Requirements for the Brownstone Over the Course of 2013

Load Requirements Over Each Month of the Year

Figure 6 Overall Load Requirements for the Brownstone Over the Course of January

Figure 7 Overall Load Requirements for the Brownstone Over the Course of February

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Figure 8 Overall Load Requirements for the Brownstone Over the Course of March

Figure 9 Overall Load Requirements for the Brownstone Over the Course of April

Figure 10 Overall Load Requirements for the Brownstone Over the Course of May

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Figure 11 Overall Load Requirements for the Brownstone Over the Course of June

Figure 12 Overall Load Requirements for the Brownstone Over the Course of July

Figure 13 Overall Load Requirements for the Brownstone Over the Course of August

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Figure 14 Overall Load Requirements for the Brownstone Over the Course of September

Figure 15 Overall Load Requirements for the Brownstone Over the Course of October

Figure 16 Overall Load Requirements for the Brownstone Over the Course of November

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Figure 17 Overall Load Requirements for the Brownstone Over the Course of December

Load Requirements Over an Autumn Day

Figure 18 Overall Load Requirements for the Brownstone Over August 14th, 2013

It is noted that temperature records over the entire 2013-year were acquired from

public records []. The coldest day in August in 2013 was August 13th. Therefore the

temperature values from this day were utilized in this analysis. All heating load

values can be found in the appendix within the code developed for heat load

analysis. In order to properly size the heating source the heating load for peak

building heating demand must be determined. One can see from Figure_ that the

biggest heat loads are in January. This directly correlates to the coldest temperature

recordings of the year that were found in January. Upon further investigation of

tabulated heat load requirement data it is determined that the biggest heat load

requirement is 34,972.977BTUhr

(2). Due to the large assumptions made in this

preliminary analysis one would expect all heat load values to be relatively low.

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Therefore this maximum value along with the other determined loads are

acceptable. This load and the corresponding lowest temperature recording in

January will be utilized to calculate the heat load requirement per room. The heat

source that will be chosen for this analysis is a natural gas furnace. Therefore the

building will be heated through forced air heating. There are many natural gas lines

located in New York City and would provide an easily obtainable source of fuel for a

heating system. Furthermore, using a natural gas furnace is efficient, and easy to

maintain. Natural gas furnaces require little maintenance. The furnace will be placed

in the assumed insulated basement area. Therefore heat generated will not escape

to the outside environment through ductwork. All the ductwork will be efficiently

placed indoors. Next, the required total airflow rate and the required airflow rate

per room from the furnace will be determined. Required heat loads and airflow

values per room can be found in the table below. It is noted that a moderate heating

air temperature of 122°F will be utilized:

Table 4 Load and Airflow Rate Requirements for Each Heated Area in the Brownstone (3)

From Table 4 one can see that the total required airflow rate is 600 cfm. Now that all

the required parameters for heating the Brownstone are known the natural gas

furnace can be chosen. For this application the Rheem Classic Series

Upflow/Horizontal Gas Furnaces have been chosen. Specifically the

R801PA050314M*A model has been chosen. Highlighted features of the model can

be found in the table below:

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Table 4 & 5 Main Specifications for Chosen Natural Gas Furnace [7]

The furnace supplies 40,000BTUhr

and an airflow rate of 651cfm while also

delivering 0.7in.wg of static pressure. This all occurs at the low fan speed setting.

Thus, the furnace supplies the required heat load and airflow rate while using

natural gas as its fuel. Furthermore, this model delivers the air in an upflow manner.

This allows the furnace to be placed in the basement space of the Brownstone. This

concludes the analysis on heating loads and the selection of the heat source.

Duct NetworkNext the required rectangular duct system will be sized in order to properly deliver

the heated air to the rooms. There are several parameters that are already known in

relation to the duct system. It is obvious that the working fluid of the system will be

air. The required airflow rate for the entire system and per room can be found in

Table 4. Furthermore the furnace provides 0.7in.wg of static pressure. Total friction

loss will be kept around 0.1in.wg per 100ft of ductwork which is a industry

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standard. The duct system will be constructed with Galvanized steel metal. This

material is usually used to construct air duct systems making fabrication easier, and

material readily available. The duct system will be connected to the furnace with a

belmouth entrance to reduce friction losses. Branch fittings will be 45° wyes, and

elbows will be 90° pleated to further reduce friction losses. Rectangular duct aspect

ratios will be kept below 4 to comply with industry standards. No diffusers will be

utilized in this analysis for simplicity. Air will be delivered to the rooms from

openings in the ductwork. The furnace will be placed directly in the path of the

hallway a foot away from the front of the Brownstone. This will allow the ductwork

to run vertically up to the 4th floor while maximizing space in the Brownstone. A

duct system should not obstruct any living space. The ductwork will branch off on

every floor underneath the ceilings. Because the ductwork is exposed to living areas

a low-velocity duct system must be designed. Therefore the maximum air velocity in

the ducts should not exceed 1200fpm. This would provide a low-noise low-vibration

system. Openings in the ductwork will be placed in the center areas of each room to

provide heating. For this preliminary analysis a return less system will be

considered for simplicity purposes. Lastly, ductwork will be considered to be well

insulated. Meaning that no heat loss will occur from the ducts themselves. Heat will

only be transferred through the opening in the ducts. A drawing of the ductwork

system can be found in the figures below:

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Overview Schematic of Developed Duct Network

Figure 19 Schematic of Ductwork Network Through the Four Floors from the Basement. Image is Shown from a Side view of the Brownstone

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Schematics of Developed Duct Networks for Each Floor

Figure 20 Schematics of Ductwork Network Running Through Each Floor to Heated Areas. Image is shown from an Overhead View

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Because the dimensions of the Brownstone are already known lengths of the ducts

can easily be determined. These lengths and airflow rates are represented in the

table below:

Table 6 Lengths and Airflow Rates of Duct Sections in Duct Network

Using the industry standard of 0.1in.wg per 100ft for appropriate friction losses and

the known flow rates the diameters and airflow velocities can be found for straight

galvanized steel ducts. It is noted that these diameters will be converted to

rectangular dimensions. Both of these tasks will be completed using duct-sizing

techniques. The dimensions and air flow rates of the straight galvanized steel ducts

can be found below. It is noted that sizing values are found using appropriate sizing

charts.

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Table 7 Diameters and Airflow Velocities for Straight Galvanized Ducts

Using appropriate sizing charts and an aspect ratio lower than 4 the equivalent

rectangular duct dimensions can be found. These values are summarized in the

tables below:

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Table 8Typeequationhere . Converted Rectangular Dimensions of Duct Sections and Airflow Velocities in Duct Network

Finally, using the equivalent length of the longest branch the supplied static

pressure from the furnace can be verified. If the largest friction loss in the system is

utilized the largest required static pressure can be determined. Thus, the furnace

will not have an issue distributing air through smaller duct branches. The equivalent

length of the longest branch is 154.41ft(4). Thus, the required static pressure is

0.151in.wg(5). This confirms that the furnaces supplied static pressure of 0.7in.wg is

sufficient. It is noted that for the very low airflow rates and corresponding loads the

ducts are slightly oversized. This is due to the lack of sizing data for very low flow

rates. For energy saving considerations these ducts should be resized using

appropriate data. This concludes the preliminary analysis of the ductwork system.

ConclusionThe heating system for a four story brownstone in the New York City area was

successfully analyzed and developed. The representative temperature fluctuations

in 2013 were accurately depicted in Figures (5-18). The calculated heat loads and

airflow requirement values are acceptable when considering the large assumptions

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that were made when developing the system. It is noted for a complete final analysis

infiltration, ventilation, and the effect of the 1st level being partially underground

must be considered. Furthermore, heat transfer analysis to the other neighboring

Brownstones must be considered. In addition for energy consumption analysis solar

heat gain, heat storage of the building, and internal heat gain must be considered.

The chosen furnace successfully supplied the heat load, airflow, and static pressure

requirements. The ductwork was successfully developed to utilize the natural gas

furnace. Maximum flow velocity requirements were met for a residential building.

This shows that the ductwork will be quiet enough for the Brownstone.

Furthermore, the aspect ratios for all rectangular ducts were kept within industry

standards. This eliminated excessive losses from the system. As stated before the

ducts in very low airflow areas were slightly oversized. In order to increase

efficiency of the system and limit losses these ducts should be resized using

appropriate charts. Ultimately the heating system fulfills all requirements for a

preliminary analysis. This concludes the report.

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AppendixSample Calculations

1) q=UA∑ , material∆T=96.34 ∆T

UA∑ ,material=UAbackwall+UAwindows+UAskylights+UAroof=96.34BTUh℉

UAbackwall=0.05∗114.92BTUh℉

UAwindows=0.25∗320BTUh℉

UA skylights=0.25∗7BTUh℉

UAroof=0.04∗210.243BTUh℉

It is noted that this is a sample calculation of the heat loss equation developed for the

4th floor bedroom. This method is utilized many more times to obtain heat loss

equations.

2) q largest=UA∑ ,total structure∆T=34971.977 BTUh

UA∑ ,total structure=613.56BTUh℉

∆T=(T i−T o )=57℉

T i=68℉

T o=11℉

It is noted that this is a sample calculation for the Overall Heat Loss of the entire

building on the coldest day of the year. This method is utilized many more times in the

analysis to obtain heat loss values.

3)cfm total=q largest

1.08 ∆T=599.67 ft

3

m

q largest=34971.977BTUh

∆T=(T i−T o )=57℉

T i=68℉

T o=11℉

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It is noted that this is a sample calculation in order to find the overall cfm requirement

for the entire building. This method was utilized many more times in order to obtain

cfm values.

4)

Le ,total=L straight+Lent+Lwye ,thru+Lcontr+Lwye , thru+Lcontr+Lwye ,thru+Lcontr+L90+Lwye , through+Lcontr=154.41 ft

Lstraight=91.41 ft

Lent=12 ft

Lwye , thru=8 ft

Lcontr=4 ft

Lwye , thru=7.5 ft

Lcontr=3.5 ft

Lwye , thru=7 ft

Lcontr=7 ft

L90=10 ft

Lwye , through=5 ft

Lcontr=3 ft

5) ∆ Pduct=0.1∈.wg100 ft

∗Le, total=0.154∈.wg

Le ,total=154.41 ft

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27

Code Developed for Heating Load AnalysisYear

28

29

30

31

Month

32

33

34

35

36

37

Day

38

Natural Gas Furnace Specifications

39

40

41

42

43

44

45

46

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References[1] McDonald, Andre, and Hugh Magande. Introduction to Thermo-Fluids Systems

Design. 1., Auflage ed. New York, NY: John Wiley & Sons, 2012.

[2] Vedavarz, Ali, and Sunil Kumar. HVAC Handbook of Heating, Ventilation and Air

Conditioning for Design and Implementation. New York: Industrial Press, 2007.

[3] "Weather History for Central Park, NY." Weather History for Central Park, NY.

Accessed December 15, 2014.

http://www.wunderground.com/history/airport/KNYC/2013/8/14/DailyHistory.h

tml?req_city=NA&req_state=NA&req_statename=NA&MR=1.

[4] "Air Heating Systems." Air Heating Systems. Accessed December 15, 2014.

http://www.engineeringtoolbox.com/air-heating-systems-d_1136.html.

[5] "Thermal Conductivity of Some Common Materials and Gases." Thermal

Conductivity of Some Common Materials and Gases. Accessed December 15, 2014.

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html.

[6] "From The Miron Blog." New York City Real Estate Blog. Accessed December 15,

2014. http://www.mironproperties.com/blog/a-short-history-of-the-nyc-

brownstone.

[7] "Rheem." Classic Series: 80% AFUE R801P Upflow/Horizontal Series. Accessed

December 18, 2014. http://www.rheem.com/product/gas-furnaces-classic-series-

80-afue-r801p-upflow-horizontal.

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