**4. Examples of successful steam heating**

The efficiency of a thoughtfully retrofitted steam heating system can match today's standards:


Besides efficiency, superior comfort can be achieved by steam heating systems even in very old buildings (1850th), − US presidents and their spouses in White House and financial advisors in the US Treasury buildings would not accept anything but the best [18, 19]. Treasury building received a LEED Gold certification in 2011 [20]. These are not tall buildings, but the technology is the same.

To resume:


*Steam Heating Conundrum of High-Rise Buildings DOI: http://dx.doi.org/10.5772/intechopen.108107*

Public fondness toward HWH is constantly fueled by complaints about noise and low efficiency of the steam heating system which continued functioning even after decades of neglect and scarce maintenance. Maybe it's more rational to find a way to optimize steam heating systems performance rather than proceed with expensive conversions? Many of steam heating buildings are more then 70–80 years old. With average building life of 120 years, such conversion is economically questionable.

#### **5. Evolved solution: nextGen vacuum heating**

Vacuum heating, − another kind of steam heating, − was very popular in the 1910th and actually preceded heat pipes concept. Heat Pipe (please, do not mistake it with Heat Pumps) – is the most efficient, resilient, and electricity independent method of heat transfer, employed in NASA spaceships since the 1970th. Basically, it's a closed ends tube under vacuum where working liquid evaporates at one end and releases latent vaporization heat by condensing at the other end.

According to the 100 years old data on steam heating conversions into vacuum heating, reported fuel savings were 30–35% [21]. Instead of pushing air from the system by steam at 2 psi, steam is pulled from the boiler by 10–25"Hg (1"Hg = 0.033421 atm) vacuum at speed of up to 150 mph (1 mph = 0.44704 m/s), which ensures quick and even heat delivery to the farthest radiators in the system. Additionally, thanks to the naturally induced vacuum in the idle cooling down system more heat is sucked up from the boiler after the heating cycle, which would otherwise be lost in the steam systems. At the same time corrosion is reduced because of limited oxygen access into the system. On top of this, steam temperature can be regulated by the vacuum level in the system, so soft comfortable heat can be delivered in warmer weather, rather than being fixed to the 214-218°F range found in steam systems. A good example is the 80+ years old vacuum heating system in the iconic LEED Gold Empire State Building. In the 2009 retrofit, instead of replacing the old vacuum system by hydronic, it was successfully restored to the original design.

The vacuum return systems were widely used to speed up a cold start of steam system heating typically in large and tall buildings. The technology was so conventional that the sale of more than 60,000 vacuum pumps was reported from a single leading supplier since 1921, with most (about 50,000) purchased prior to 1980 [22]. Most of these abundant systems are still around waiting for upgrade/retrofit.

Unlike Heat Pipes, today's vacuum heating is actually a "pseudo" vacuum; the vacuum section of the system is separated from the section under steam pressure by a steam trap behind each radiator(s). These required steam traps present an ongoing maintenance problem. Steam traps on radiators last only 10 years at best, and are often ignored when they fail because of the expense and annoyance of repair. Steam leaking through a single failed trap (out of hundreds in tall buildings, − 6600 in Empire State Building) overloads the vacuum pump, condensate pump, etc. The result is unbalanced, noisy, and very expensive systems. Compared to many other vacuum systems that gave up after a multi-year struggle, Empire State Building definitely excels in steam traps preventive maintenance.

For existing steam/vacuum systems steam traps, this problem can be resolved by converting existing steam/vacuum heating into NextGen vacuum heating system. Observation of vapor and condensate flowing through the transparent plastic piping in the vacuum heating system revealed surprising insights. It turned out, the vacuum system can self-balance quickly and evenly with proper system design [23]. The trick


#### **Table 1.**

*Result of steam heating retrofit pilot study.*

is to prevent steam "short passing" toward the vacuum pump. This has inspired a new "steam traps free", entirely under the vacuum system paradigm [24]. Pilot study confirmed fuel gas savings for two different systems used to heat the same apartment – **Table 1**. Energy efficiency of the original single pipe steam system (~100 years old boiler, piping and radiators) was compared to the same boiler connected to new flat panel radiators by copper/plastic lines; the same comparison was carried later on new regular steam boiler. While boiler upgrade in steam system saved 16.2% energy, 32.5% savings were achieved in vacuum system. Up to 50% in savings was demonstrated by the complete retrofit from steam into a vacuum heating system [25]. In the winter of 2014–2015 results were confirmed.

Steam heating systems in tall buildings are either 2-pipe steam or 2-pipe vacuum heating systems. Without any contempt for the great planning and implementation of the 179 Henry street. NYC project, imagine now that the same building was converted into new vacuum heating system:


This is a minor job compared to the complete replacement of existing steam boilers, piping and radiators by hydronic, on the top of adding mechanical floors

*Steam Heating Conundrum of High-Rise Buildings DOI: http://dx.doi.org/10.5772/intechopen.108107*

(for skyscrapers higher than 20 floors), circulators, PRVs, etc.; not to mention the disturbance of tenants, − the main reason why most retrofits are indefinitely postponed.

For the systems with old piping, the majority of leaks are at supply valves near the radiators and can be fixed. In our experience with three retrofits of residential systems (all are 100+ years old steam heating) no major leak was found in the pipes. Minor leaks from hidden inner-wall piping are inevitable, but the problem can be resolved by converting the steam system into a "vacuum boost" heating system. Here, steam quickly and evenly fills the system under vacuum, raises the pressure to 1–2 psi (to avoid air leakage into the system) and continues to heat the building at low positive pressure till the thermostat is satisfied. Retrofit into "vacuum boost" technology does not require frustrating efforts of leak detection and repair. For "cold" vacuum sustaining test a drop from 20 to 5"Hg in 2 hours is acceptable, compared to a 20–18" Hg drop in 2 hours required by the Vary-Vac – the most popular today's vacuum heating system.

Compared to HWH, leaks in a vacuum heating system are much less of a problem - no water flooding to the lower floors and expensive repairs. The only moving part in the NextGen Vacuum heating system, − vacuum pump –is never exposed to steam and is employed in 5–10 minutes intervals for 1–1.5 hours daily. With a 5–10 thousand hours warranty time and average of 4 month winter season, life expectancy is in a 37–75 years range until the first needed repair/replacement. Condensate is returned into the boiler by gravity; in case of district steam, by a designated pump.
