Nelson Mechanical Design Martha's Vineyard Green Contractor
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Nelson Mechanical Design
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HVAC Design & Installation for Residence and Business
HVAC (Heating, Ventilation, and Air Conditioning) systems offer a flexible platform of comfort and air quality options that hydronic heating systems cannot. Heating, cooling, air filtration, dehumidification, humidification, and exhaust and fresh air exchange are just some of the features possible with a HVAC system.
Ducted Systems
Our ducted systems consist of insulated sheet metal trunks and insulated flexible branches (for sound attenuation). We size all of our duct work with Building Systems 2007. This is a CAD program that gives us duct sizes and drawings for the actual developed lengths of the ducted system. These designs are based on our heat losses and gains that we calculate with Elitesoft RHVAC software. The result is a completely organic system that operates at low velocity and is virtually unnoticeable.

PDF of Heat Loss
PDF of Building Systems 2007

Sheet Metal
All of our supply and return trunks consist of insulated sheet metal duct. This material has great durability and is a very clean product. Some of our competitors will keep costs down by using a pressed fiberglass duct that has some health concerns and is not nearly as durable.
Flexible Runnouts
All of our supply branches consist of insulated flexible duct with an insulated rating of R6 and a foil faced outer lining. When installed correctly, this product saves labor and time.
Heating
Cooling
Our warm air systems can provide heating using a furnace, air handler, or heat pump type system. One bennefit of a warm air heating system is it's quick response. For example, if you were to keep the heat down to 55 degrees while you were out, the system would be able to respond quickly when you need it. Our cooling system can provide air conditioning using traditional air conditioning equipment, chilled water hydroair, inverter drive technology, or geothermal technolgoy. One benefit of cooling is it's natural dehumidification process.
Air Filtration
AIR FILTRATION: All of our ducted systems are installed with HEPA grade filters. Electronic and ultra violet filters are available for our customers who desire a higher level of air quality.
Dehumidification
DEHUMIDIFICATION: Dehumidification is very important in our homes and businesses. Dehumidification provides comfort, prevents mold growth, and protects fine finishes and equipment. There are several different ways to achieve dehumidification.
Whole House Dehumidifier By Cooling

WHOLE HOUSE DEHUMIDIFIER: We install this type of system when there is no cooling system to passively dehumidify the space. We install several small ducts to pull moist air from the living space and return dry air to the space.

BY COOLING: A natural benefit of cooling is dehumidification. Some days of the year, dehumidification is desired but cooling is not. In this instance, we can provide what we call Reheat. Reheat is the dehumidification of the space using a cooling cycle and then the Reheating of the space with a heating cycle.
Local Dehumidifier

LOCAL DEHUMIDIFIER: We install a local dehumidifier in almost every mechanical room. We set up our dehumidifiers with an automatic pump, so the equipment never needs to be emptied. Every basement should have one!

Humidification
HUMIDIFICATION: Humidification is one of the great benefits of our ducted systems. Humidification is very important in the dry winter months for both comfort and health concerns. We can achieve humidification in two ways:
Steam Humidification Evaporative Wheel Humidification
STEAM HUMIDIFICATION: Steam humidification is one of the best way to add moisture to your living space. We will install a steam humidification unit on the supply trunk of your air system. This will be controlled by a humidistat (similar to a thermostat). Our steam humidifiers use a back flush system that reduces scaling and increased electrical usage. EVAPORATIVE WHEEL HUMIDIFICATION: A very cost effective way of adding humidification to your air system. Evaporative wheels passively add moisture to the dry air that is passing through your warm air system.
Fresh Air Exchange
Commercial Systems
FRESH AIR EXCHANGE: As much as we try to fight the infiltration of the harsh outdoors, fresh air exchange is necessary in public commercial buildings and residential buildings with substantial insulation. Even though we want to build our structures with the best vapor barriers and insulation on the market, we still need fresh air as a part of our necessary comfort levels. Fresh air intake must be accounted for in the heat loss/gain calculations for the building and the heating and cooling systems must be able to handle this load. COMMERCIAL SYSTEMS: Almost every public building requires a certain amount of fresh air to be introduced to the building envelope. Building codes usually require 15 cubic feet per minute (cfm) of air per person. Introducing air from the free atmosphere into a conditioned building requires a great amount of design and knowledge to ensure that it will work well with other air systems such as exhaust hoods.
Residential Systems
RESIDENTIAL SYSTEMS: The construction of the residential envelope is getting tighter and tighter. Products such as icynene, high density spray, and cellulose insulations are creating little or no infiltration into the building. This is great way to reduce the heat loss/gain of a building. However, fireplaces, gas appliances, and the finishes of a building require fresh air to function correctly.

In the residential application, we eliminate the bathroom exhaust fans normally installed by the electrician. We replace these exhausts with ductwork that will connect to the heat exchanger in an ERV (energy recovery ventilator) or HRV (heat recovery ventilator) unit. From the unit, this exhaust will continue and terminate to the free

atmosphere outside. We then bring in fresh air from outside through ductwork that is also connected to this unit. It crosses through the heat exchanger, picks up the heat from the outgoing exhaust air, and is delivered to an alternate location of the building, or into the supply of the warm air/cooling system. This unit is then activated with the same electrical switch installation that would normally power the electrician’s bath fan. In the summer, operation can be reversed and warm fresh outside air can be cooled by outgoing cool stale exhaust air.

See our Hydronic Heating page 1: Hot Water Boilers and Radiant Floor Heating