E-House: Toward The Perfect Mechanical System|
“Light Catchers” Installed At E-House: During Construction In The Mid-Hudson Valley North Of New York City.
Michael Mcdonough, AIA, NCARB, Lloyd Hamilton and Sephir Hamilton
Posted on: 01/10/2005
Michael McDonough, AIA, NCARB recalls:
The idea for e-house occurred to me sometime in 1999. Simply put, it
was the fact that everything required to build a perfect vision of the
future was actually available now. Anything a forward-thinking
architect could imagine was invented, manufactured, packaged,
searchable on the internet, purchasable with a credit card, and
The green, sustainable technologies that could make for an
energy-efficient future were there: super-efficient insulations,
radiant cooling systems with geothermal hook-ups — you name it. Smart
building controls were there, too: enough software, sensors and
networking capabilities to run an entire building automatically. A
house could monitor fuel efficiency while you watched a movie.
The problem was that all these wonderful things were unavailable in
one coherent, marketable, understandable package. It was as if you had
stumbled across a 10,000-piece jigsaw puzzle of the Mona Lisa, but the
cover of the box was missing and the pieces were all over the floor.
You could tell it meant something important, but it would be quite an
exercise to form a clear picture.
I had seen this incoherency for decades. First, I studied and worked
with environmental artists in the 1970s and they taught me about the
lyrical, image-making power of nature and built form’s response to it.
All this while the rest of the world was dancing to disco.
I also saw the same short-of-the-mark efforts of enlightened
businesspeople and manufacturers throughout the 1980s and 1990s. Small
companies offered amazing recycled content, energy-efficient and
nonpolluting products: soybean wall tiles, high-strength cellular
recycled paper construction panels, hemp particle board, bamboo
As often as not, these products would start in someone’s garage, and
be withdrawn from the market with the company in bankruptcy, just after
the product literature was finally distributed. Some large companies
offered green products, but didn’t market them as such, often because
they believed that talking about sustainable technologies was
irrelevant, and that it would have no impact on sales.
Fast forward to the turn of the 21st century. Amazingly, a lot of
green technologies have somehow survived, and new ones keep popping up
all the time: new concretes, recycled blue jeans insulation,
sustainable forestry lumber, healthier paints, formaldehyde-free
building panels, and so forth.
Traditional building techniques (so-called “alternative”
technologies) now are recognized as having value in terms of energy
efficiency, local materials sourcing and cultural identity. Operable
windows and high-efficiency fireplaces have a place in the future, only
now they are “fresh air delivery systems” and
E-house — located in the mid-Hudson Valley north of New York City —
is the manifestation of these ideas. Stylistically, it is both
contemporary and traditional. Big, sculptural trapezoids are
cantilevered off a traditional stone-covered core.
the roof deck has a monumental south-facing stair. Jammed with
technology, embodying craft, I like to think of e-house as a model for
the future of building — not so much the shapes, but the “adjust to
nature” ideas behind them.
Dozens of people have contributed to the development of e-house, but
a few deserve special mention here. The internationally renowned
engineer Valentine Lehr provided early encouragement regarding the
mechanical system’s concepts. The father and son team called Verdae has
taken on the mechanical system fine-tuning, number-crunching and
installation tasks at e-house, and have joined me here as co-authors.
Peter Caruso of monitor products put us on a technology diet, guiding
us into the simplest iteration of a complex system. Bruce c. Duffy
serves as project manager, forever cracking his brilliant, polymath,
This article is an exploration of e-house’s energy-efficient heating
and cooling technologies, and its transformation from a gleam in my eye
to what we collectively like to think of as a high-performance building
leaning toward the perfect mechanical system.
the e-House model, the perfect heating and cooling system would be
based principally on human comfort factors. It would always feel like a
spring day indoors, and the human skin would be the great arbiter of
|Artist's rendering of eHouse at completion.
In other words, “If it don’t feel right, it ain’t right.”
Sure, from a technical point of view, it would be energy-efficient and
multitask wherever it could. It would make full use of all waste heat,
store energy for future use and allow for both passive and active
systems. It would ideally control itself, using high-tech controls and
building intelligence, but would be based on readily available
software, and simple temperature and humidity sensors. It would have
super-sophisticated systems where it needed them, but would also make
use of time-tested (“alternative”) technologies when they did the job
Those are our assumptions, and — bearing in mind everything has to be
ordered over the Internet, available now, shippable now and ready to go
“out-of-the box” — this is how we see it (and how we are building it)
Think of e-House as a high performance building first and foremost. It
is a super-tight, super-insulated, “green” building. Moisture in the
building — water vapor — is controlled through carefully engineered
sequences of materials acting as vapor diffusion resisters (in industry
parlance, VDRs). This means that the interior finishes, the core
materials of the walls (SafeCrete autoclaved aerated concrete and
Winterpanel structural insulated panels), exterior finishes, the
insulation in the roofs (Applegate recycled paper cellulose), and even
the roof assembly all are designed to complement each other, and to
allow the building envelope to move moisture out of the core to the dry
side of the wall.
“passive” whole-house moisture control systems are complemented by
active mechanical ventilation: a fully balanced, whole-house system
operating on neutral building pressure, and a state-of-the-art
Nutech/Lifebreath Energy Recovery Ventilator/Heat Recovery Ventilator
(ERV/HRV) system that provides full fresh air all year long while
saving energy — superb indoor air quality at bargain operating costs.
The passive and active systems meet up at motorized windows (carefully
placed as high-up and low-down in the structure as reasonably possible)
that can fully purge the building’s air in about five minutes (about 12
air-changes an hour).
is set at 6-inch centers at tiled bathroom and shower to provide
slightly warmer floors. Screed here is adjusted to 1 inch. Mapei
thinset and grouting, and Tulikivi “naturally non-slip” soapstone tile.
Retaining Maximum Energy: Because energy efficiency counts for so much
in e-House, the emphasis is on retaining both maximum harvested and
generated energy. An in-ground cistern (under a summer kitchen and
terrace) acts as a ground-coupled thermal reservoir, collecting
rainwater and storing warm or cool water rejected by building systems
during normal operation.
A WaterFurnace water-to-water geo-exchange heat pump allows this energy
to be employed for domestic hot water preheat — this using Amtrol's
StorageMate™ in conjunction with its new BoilerMate EZ Series and
Extrol Expansion Tanks — or for snowmelt functions. And a WaterFilm
Energy Inc. drain heat recovery unit cuts the hot water cost of a
typical shower in half.
Truth be told, initial construction costs would be higher than a
typical home, but not out of line with custom home costs. But we also
are thinking long-term here. Lower operating costs and multitasking
strategies allow the system to “fire on all cylinders” with tremendous
efficiency 24/7/365. The cistern, for example, provides irrigation for
gardens (we get an average of 30,000 to 40,000 gallons of rainwater off
the roofs and terraces each year), and a dry-plug for exterior fire
suppression. The real fire suppression system would be indoors;
however, its distribution system is no bigger than 1/2-inch diameter
coils of potable water PEX. That is because it would be an extension of
the building’s Uponor Wirsbo AquaPEX potable water system, looping
through the ceilings, connected to recessed sprinkler heads. Note that
our “good old-fashioned potable water well” multitasks, introducing
ground-temperature water, lowering cistern temperature when necessary.
(The boiler, which would use the cistern as a preheater, can raise the
cistern’s water temperature at the geo-exchange heat pump when
outside, the south-facing roofs and roof decks have mechanical system
(as well as rainwater collection) functions. Roof decks are covered
with a unique nonslip exterior grade porcelain tile that sits on
PEX-grabbing insulation and uncoupling membranes by Crossville and
Schluter, respectively. These tiled and insulated view platforms double
as deer-proof potted plant herb gardens, and three-pete as snowmelt
systems, solar collectors and solar diffusers (depending on the
he-PEX and sensors are set into the floor assembly using a special
screed of slag-based concrete to maximize thermal mass. Note the PEX is
placed 8-inches-on-center between 1 1/2-inch high sleepers that also
form guides for the screed.
Nonroof-deck roofs both shed their rainwater into the cistern, and
capture air and rain water pollution by bonding it to Follansbee’s
stainless-steel and zinc roofing. The roofing doesn’t decay when
exposed to pollutants; it gets stronger.
Interior comfort heating and cooling are provided through the floor
assembly using a constant circulation hydronic system (also by Wirsbo,
with Danfoss controls) and an LP-gas-fired sealed combustion boiler
(MZ-25C by Monitor Products with no required annual maintenance and a
near-zero failure rate). Venting is Z-Flex by Z-Vent, with selant-free,
fail-safe gasket and locking band connection. The infloor system
features he-PEX set in concrete that is, in turn, sandwiched between
two layers of oriented strand board and topped with white oak wood
flooring. e-House can feed either warm or cold water through the
floors, or harvest passive solar heat from southeast-facing windows
through the same high thermal mass radiant floor assembly.
and humidity sensors let e-House’s building intelligence computer know
where the system is hot and where it is not, at both interior and
exterior conditions. In full-bore building intelligence mode, the
computer gathers data from the sensor, making decisions as to what goes
where, mixing and shunting energy back to the manifolds and controls
for redistribution throughout the building. |
If you think this sounds far-fetched, just remember that the e-House
uses a small fraction of the computing power needed to, say, start your
car in the morning or deliver an e-mail. We need to ask more from
building intelligence; the capabilities are there.
The radiant industry tells us that radiant cooling works, but in humid
conditions, dew point and condensation issues make it a risky choice.
Radiant ceilings, it also notes, require condensate gutters, and you
have to construct PEX-based ceiling panels or install manufactured
radiant ceiling panels — in addition to the infloor systems for heat.
No matter what, the dew point must be kept below the temperature of the
circulated cooling fluid. Radiant floor temperatures have to be
strictly controlled, and condensation at a floor-based system is even
more important, because the floors will get slippery fast and warp over
a period of time. (Ceilings just drip.)
Not In My Backyard: So why infloor radiant cooling at e-House? We like
installing one radiant system rather than two (floor vs. floor and
ceiling), and we like a challenge. But we also like to hedge our bets:
“Conventional” construction can “leak” (i.e., allow thermal, air and
water vapor to move along virtually uncontrollable and undetectable
pathways) so much that it is very difficult to fully dehumidify a
e-House’s high-performance, super-insulated building envelope, however,
allows us to control thermal, air and water vapor infiltration and
exfiltration. This allows us to “deep dehumidify” first (before we
cool), ultimately reducing our cooling load by as much as 70 percent,
while the house remains free of condensation.
e-House’s deep dehumidification is achieved by a simple chilled water
coil within the ERV-HRV ducted air flow. And it is that airflow —
specifically displacement ventilation — that completes the big
mechanical system picture here. Conventional wisdom teaches us that hot
air rises and cool air sits on the floor. Fluid dynamics and
displacement ventilation principles, however, redefine the conventional
In e-House, displacement ventilation encourages air temperature to
stratify like a thermal layer cake — warmest on top, coolest on the
bottom. Ducted, recirculated interior air enters the space along and
across the floors, creating subturbulence that engineers would term a
“nearly laminar” flow. This is more typical of viscous fluids than air.
As it is (barely) churned up and warmed, the air moves up into these
stratified zones, displacing the air that was there before it.
In other words, a little bit of strategically ducted air can shake up
the air in the thermal layer cake, but not the air temperature.
Relatively low loads, low volume and low velocity ensure that the
stratification isn’t extreme enough to be perceived as uncomfortable.
Also, we are still primarily a radiant cooling system, cooling objects
in the room. Displacement ventilation is focused on the relatively
minor convection components of the radiant system. Also, at e-House, a
return-ducted negative pressure point exists at the high point of the
building’s relatively open floor plan. Indoor air pollutants and odors
are captured here, then filtered and recirculated though the ducted
ERV/HRV system. Except for 200 CFM of bathroom exhaust and a kitchen
ventilation hood with balanced make-up and exhaust air, what goes
around in this system comes around — literally.
In other words, a little bit of old-fashioned convection mixed with
state-of-the-art deep dehumidification can go a long way in radiant
floor cooling, making it comfortable enough for a hazy, hot and humid
day in late August. One side note: Thermal plumes from people,
equipment and sun-exposed floors will turn cold air into warm air that
(again) moves upward — like little thermal “worm holes.” (“Star Trek”
to e-House’s “alternative” technologies, the exterior finishes are
wide-mortared, semi-coursed, site-sourced stone and back-primed cove
siding — a tip-of-the-hat to local building traditions. (We also get
additional thermal mass, drainage planes, increased R-factors and wind
breaks from these humble technologies.)
The roofs and roof decks move their rainwater down and into the cistern
using scuppers, leaders and simple gravity. All the windows are
operable and screened. Passive solar glazing is on the south and
southeastern sides of the building. This is countered by roof overhangs
designed as shading devices. All rooms have day lighting, all see the
first light of dawn all year long (even if it is reflected off a wall
through a monitor window), and every room has cross-ventilation.
A great room on the main floor contains kitchen, dining and living
spaces, and is modeled on traditional farmhouses, complete with a
wood-burning fireplace and bread oven. But these have super-insulated
(Isokern and Dura-Tech) chimneys and feature a 200-year-old
Rumford-style fireplace finished in highly heat-reflective soapstone.
Most of the time, a few logs in the Rumford along with the occupant,
lighting and equipment loads will heat the place in winter, and
cross-ventilation from open windows in summer will keep things cool
enough to be comfortable. We figure we need about 10 Btus per square
foot at minus 20 degrees F with a 20 mph wind. No matter. The cistern
spent the summer collecting heat for that chilly day, when it comes.
Sidebar: e-house for wet heads|
e-house heat loss modeling was based on the next-generation of DOE-2
software, called Energyplus (www.energyplus.com). This allowed us to
get an hour-by-hour, day-by-day energy consumption model of the
building, and informed the design of all systems. We were specifically
able to understand heating and cooling loads and the sensible heat
ratio, which runs as low as 0.60.
floor temperatures have to be strictly controlled, and condensation at
a floor-based system is even more important, because the floors will
get slippery fast.
- e-house has a 30,000 btu/hr. Peak heating load, but almost 50 percent
of that is through high-performance windows comprising less than 13
percent of the building envelope surface. In a worst-case scenario,
less than 5 percent of the heat loss is from infiltration, 20 percent
from ventilation and 25 percent wall/roof heat loss.
in other words, the high-performance building envelope skews the
relative percentage of the window heat loss upwards; we fight back with
automated window quilts.
- the 4.5-ton peak cooling load is about 30 percent solar, 20 percent
window heat gain, 30 percent internal loads, 15 percent roof and walls,
and 5 percent infiltration and ventilation. Here again, the
high-performance building envelope skews the relative percentage of the
window heat gain upwards; we fight back with automated sun shades.
- e-house gets dry air delivered along its floors at ~68 degrees f all
year-round (cf.: displacement ventilation). It uses a dehumidification
coil and reheat coil in summer, and a heating coil in winter. In
summer, the flow rate is sized for adequate dehumidification and fresh
air; in winter, the flow rate is sized for fresh air needs only.
- e-house supply and return grills are specially designed and
fabricated to have minimum visual impact, and to keep face velocity low
to avoid turbulence noise.
- e-house has a high central ducted return that takes advantage of
natural buoyant airflow to trap air pollutants near the ceiling using
(coarse) in-duct filters; this before the stale air is recirculated
though additional filters, and then returned.
- e-house employs a constant circulation hydronic radiant system with a
thermostatically modulated zone control, allowing for optimal comfort
and control and maximum efficiency.
- e-house mechanical control systems employ a SACDA (supervisory
control and data acquisition) model employing temperature and humidity
sensors. The sensors signal a whole-house building intelligence
computer through data acquisition cards and a user-friendly
internet-based guide based on decision tree optimization, modulating
valves open or close to allow more or less flow, keeping individual
rooms within set-point.
- the e-house constant circulation system will allow the light catcher
(which is also the passive solar sun catcher) to give up its excess
heat during the winter and have it distributed throughout the house.
With this system outside, reset is not needed.
- e-house building envelope is so tight and so well-insulated that the
fast changing peaks and valleys of building load associated with
outside temperature in a conventional house are just not a factor. The
room sensors will tell us as the load changes, and the change will be
so slow that the high-thermal mass floors will have no problem keeping
in fact, we expect the slow change of floor temperature will closely match the slow change of building load.
- e-house understands that doors get left open, fireplace chimneys leak
and some stuff just doesn’t work. Plenty of cured firewood is available
on site, and a photovoltaic battery back-up system is central to our
idea of efficacy. We like computer technology, but admire the work of
the late Neil Postman, author of “informing ourselves to death,” an
essay about the disadvantages of computer technology.
Hamilton is principal of Verdae LLC (www.verdae.com), a sustainable
practices engineering consultation firm located in Poughkeepsie, N.Y.
Lloyd Hamilton is a partner in Cornacchini Construction in Rhinebeck,
N.Y. Sephir holds a Bachelor of Science Mechanical Engineering from
Clarkson University and Master of Science Mechanical Engineering from
Massachusetts Institute of Technology. His primary areas of expertise
are whole-building energy design and analysis, room air-flow, and
thermal system design. Lloyd has over 25 years of field experience in
plumbing, building performance, radiant hydronic and other mechanical
systems, is an IGSHPA accredited installer of geoexchange systems, and
a charter member of Building Performance Contractors Association of New
Michael McDonough, AIA, NCARB was educated at the University of
Massachusetts, Massachusetts Institute of Technology, and the
University of Pennsylvania. He has specialized in sustainable practices
architecture for more than 20 years, and has designed projects
internationally. Widely published, he has won citations from the
American Institute of Architects and Industrial Design Society of
America, and has written for the New York Times, ID Magazine,
Metropolis, Metropolitan Home, Builder, Wired, and other publications.
He also authored “Malaparte: A House Like Me,” and coauthored “The
Smart House” with James Grayson Trulove. Visit him at
This feature article was originally published in Plumbing &
Mechanical's July 2004 issue. The e-House was also featured in ED+C in
the January/February 2001 issue.