Topics in Photographic Preservation 2007, Volume 12, Article 30 (pp. 224-238)

Cold Storage Options: Costs and Implementation Issues

Sarah S. Wagner

Cold storage has long been recommended for the preservation of unstable film and color photographic media. This article discusses the relative costs of various cold storage options and some associated operational issues. Due to space limitations in this article, important issues related to the safe implementation of cold storage, such as specific detailed protocols for vapor-proof packaging, handling, and maintenance, are not discussed.

The benefits of cold storage are that it:

Cold Storage Options

This article discusses the relative costs of various cold storage options:

Factors Affecting the Selection of an Appropriate Cold Storage Option

The type(s) of cold storage that an institution might select depends on many factors, including the costs to implement, maintain, provide security, and protect from fire or other hazards. Institutions must weigh the advantages of one option over the other based on the

Determining Space Needs for Cold Storage

It is useful to calculate the storage needs based on the space the collection currently occupies if standard shelves or cabinets of the same type will be re-used or purchased for a new vault. Where this is unknown or not easily calculated, a helpful starting point is a conversion table for various formats. The U.S. National Archives conversion tables for films and prints are an example (http://www.archives.gov/records-mgmt/publications/audio-visual-records-inventory-form-instructions.html):

Est. #Photographic Media/Cubic Foot (CF)

Photographs Items/CF Motion Pictures Items/CF
4×5-inch negatives 2184 35mm reels (1000’) 6
35mm slides 8640 16mm reels (1200’) 11
6-frame 35mm strips 2300 16mm reels (800’) 15
8×10-inch prints 2350 16mm reels (400’) 32
4×5-inch prints 9400    

Each collection presents various formats, housings, and containers that influence its total space requirements. The actual number of items that will fit into one cubic foot (CF) may vary depending on the types of enclosures and containers, thickness and format of the photographs, distortions, mounts, etc. Likewise, the actual usable capacity of a cold storage unit can vary from 30–70% due its internal dimensions and shelving configurations. In practice, a 20-CF household freezer may only have an actual usable space of 15 CF because approximately 5 CF are occupied by shallow door shelves/bins.

Practical experience demonstrates that approximately 250 negatives that are housed in seamed paper envelopes will fit within a standard 12-inch “shoebox,” four of which can be stacked in one CF for a total of 1000 negatives/CF. However, constraints of freezer design and shelf configuration allow only 40 standard shoeboxes to be shelved in an unmodified 20-CF household freezer, not the expected 80 boxes. This halves the effective capacity within the freezer to 10 CF, or only 500 negatives/CF. The actual capacity of a 20-CF freezer would then be 10,000 4×5-inch negatives, not the estimated 20,000 based on total freezer volume or the 43,680 predicted by the conversion table!

Estimated Costs of Various Cold Storage Options and Associated Issues

For the purpose of this article, the cold storage options were limited to leasing commercial space, two vault sizes and climates, and a 20.3-CF household auto-defrost freezer. To simplify the cost calculations for packaging, shelving, and total cubic feet of records' storage, only one collection sample type was used to calculate these estimates: this one-cubic foot sample consisted of four standard 5“H × 6″W × 12″ D shoeboxes. It was assumed that each box holds 250 negatives in paper envelopes (1000 negatives/CF).

Additional assumptions included:

All costs listed should provide an idea of relative expense among various options. Costs have been calculated per CF to provide easier comparison between options. Prices will vary among vendors and regions, and do not include every possible cost involved. Costs are constantly changing depending on materials, energy, delivery (freight) charges, and labor; these estimates were obtained during the summer/fall 2007. Because quotes were based on the generic, hypothetical options requested, vendors emphasized that their estimates were approximate only due to the variable and unknown factors.

Leased Commercial Space

The leasing rates of a commercial cold storage facility were provided by one vendor with a track record for well-maintained vaults and reliable shipping and handling (Table 1). Because of the variability and efficiency of shelving among formats, large-volume leasing was quoted at a maximum rate. Actual costs for collections with uniform containers or compact containers may be lower. Handling fees will vary with geographic region and usage rates as items are requested, while the variety of formats may influence any fees for the initial shelving and bar coding. Leasing rates for 20–360 CF range from $69–96/CF/year depending on storage climate and quantity. Large-volume leasing rates for 1000–2000CF were estimated to be less than $25/CF/year.

Although cost effective at the CF level, leasing is expensive over time due to the recurring cost and additional fees for handling and shipping. However, leasing space may be cost effective for large collections that lack space, upfront resources for vault construction, ongoing resources for annual energy and maintenance costs, and/or experienced staff to operate a vault. Leasing can also be useful as a temporary solution to preserve rapidly deteriorating materials until an institution can implement permanent cold storage. Overnight shipping from distant sites delays access, although not significantly more than some standard institutional handling protocols used to warm materials prior to use.

Vaults

A firm that has installed several institutional vaults in the Washington, D.C. metro area supplied pricing for several vault sizes (8’ × 12’ × 8.5′H, 16’ × 24’ × 8.5′H, 6’ × 6’ × 8.5′H vestibule) at 35°F and 25°F, with and without 35% RH control (Table 3). Operational costs for energy and maintenance are listed in Table 2. Very low-temperature (0–10°F) vaults were not estimated due to their cost, energy demands, and substantial user discomfort factor.

The equipment specifications included standard 4-inch thick foam-insulated metal-skinned panels for walls, ceiling, and floor; air-chilled coolers, compressors, condensers, desiccant wheels for RH-controlled vaults, backup units for RH-controlled vaults, light fixtures, delivery, and installation. Fire suppression systems and remote environmental monitoring alarm systems were not included in the specifications. Gaseous air filtration also was not estimated, although this might be desirable when packaging is not used for collections, such as acetate film, that might emit contaminating gasses. For the purpose of determining cooling loads, it was assumed that the vault would be placed in an area with office-type conditions, rather than outdoors or in a more variable sheltered space such as a loading dock or covered garage, and that the space did not require modification, had ready access to utilities and that exterior mechanical systems could be located within a 75-foot run line. These and other factors could affect the estimates and overall costs. Therefore, these estimates must be considered minimum approximate costs.

Depending on their climate conditions, cost estimates for 8×12 vaults range from ˜$22,500–39,000 while 16×24 vault costs range from ˜$61,000–85,000. A 6×6 vestibule (35°F /35% RH) costs $31,500. In actuality, an acclimation vestibule serving either a 35°F or 25°F vault adjacent to ambient office conditions would be set at ˜50–55°F/35% RH and would cost slightly less than quoted. Cost estimates for annual equipment maintenance range from $500–1000/year when performed in-house (estimated by the vault vendor) and up to $4000/year for an annual service contract that provides bimonthly inspections and routine maintenance (as reported by a facility manager for a government institution).

Vaults are more cost effective in larger sizes. Taller vaults with high-tiered shelving may provide even lower cost/CF with only a small increase in initial cost.

Free-Standing Freezer Units

A Sears Kenmore auto-defrost 20.3 CF Household Freezer (˜$700) was the baseline unit used for this study, along with the Onset HOBO data logger ($300) with auto-dialer and remote alarm (Table 4). Alarm hook-up to a facility-wide monitoring system, where available, costs 2 −3 times more than an auto-dialer (˜$1000/unit). Household models tend to be reliable (when rated by consumer groups) and readily available, replaced, and serviced. The unit is 32″W × 28–1/2″D × 70″H, with shelf dimensions 26″W × 17″ D, and temperature range from 0–25°F. Large-quantity discounts were not factored into the estimates. Commercial (restaurant and scientific) freezer units are other freezer options and are available in 40- and 70-CF capacities. They were not selected for this study due to several factors including noise, heat, smaller doors (in a few models), some reported reliability issues, and expense (3–6 times more per unit and 2–4 times more per CF). However, they can be useful in some circumstances where a larger interior capacity and/or dimensions are required.

Freezers can be a cost-effective option for small collections. Institutions with limited resources can acquire freezers and the necessary packaging for rapidly deteriorating portions of the collection as funds allow. This approach may ensure the preservation of the most vulnerable items, such as deteriorating films, until they can be duplicated or cold vaults constructed. Freezers also can be used to complement vaults where only a small proportion of the collection require very cold temperatures and the remaining less-vulnerable collections of mixed media or composite works are safe in RH-controlled cool vaults (45–60 °F). Vapor-proof packaging of materials stored in freezers is discussed in the section on microclimate protection (see below).

Microclimate Protection: Vapor-proof Packaging and Sealed Cabinetry

Materials stored in freezer units and vaults without RH control require protection from RH extremes and condensation if the containers are not airtight, as is the case with well-sealed plastic and metal film cans. This can also be accomplished with either vapor-proof packaging (bagging) of boxes or the use of sealed cabinetry in vaults. To maintain a stable microclimate in a gasket-sealed cabinet, Henry Wilhelm and Mark McCormick-Goodhart recommend using conditioned silica gel or desiccated paperboard inside as a humidity buffer [1]. They also modify the vault so that the fans are timed to operate with the compressor cycle resulting in a consistent ˜60% RH within the freezer vault-thus minimizing the RH differential that the buffering material must counteract.

For a direct cost comparison between packaging and sealed cabinetry, materials and labor for vapor-proof enclosures and new standard open shelving were estimated along with sealed-cabinet costs. However, neither the labor costs to prepare the buffering material nor the cost of the silica gel or desiccated paperboard was estimated for the cabinet method.

The vapor-proof package is based on a design used by the author, incorporating a low-cost, heavyweight (6 or 8 mil) re-sealable polyethylene outer bag and an inner flush-cut bag of translucent polyethylene/polyester laminate with a metallic deposit, both sized for the standard 4×5 “shoebox.” Both bags can be re-used indefinitely until damaged. Also included was clear acrylic 2-inch-wide tape to seal over the flush-cut bag and one RH indicator card per package. These packaging materials are available in bulk from Uline and other vendors. The cost of this packaging (˜$1.90/box) is about midway between using two poly bags alone or a polyethylene outer bag with an inner metal foil-laminate plastic bag (such as used at the National Gallery of Art). Due to the durability and high-quality seams of these bags, the cost of desiccated paperboard inserts between bags was not estimated due to the greater expense and labor. Shipping costs were not included, but discounts were calculated for larger CF quantities (greater discounts may reduce costs further). Labor for packaging was based on two different levels of packaging productivity and federal hourly rates (GS5 and GS7, Washington, DC region, Tables 4). Using these low- and high-labor rates of $120.00/day and $200.00/day, total packaging costs ranged from ˜$5.50/box to ˜$8.75/box, respectively.

Shelving and Cabinetry

Furniture estimates were provided by suppliers of museum-quality shelving and cabinetry, and included fixed and mobile units delivered and installed. (Tables 3 and 5) The costs for silicone gasket-sealed cabinets were based on units 39.5″W × 17.5″D × 84″H (Table 4) with seven 12″H shelves. A larger cabinet, 58″W × 32″D, would offer an advantage for oversize items (at a base cost of approximately one third more). Discounts for larger cabinet orders were quoted along with reduced freight charges. The cost of a mobile cabinet installation was not quoted by the vendor and was approximated by the author. Standard open shelving estimates were based on units 36″W × 12″D × 84″H with seven 12″H shelves. The vendor provided cost estimate ranges for delivery and installation for both fixed and mobile configurations. For the purposes of this article, the estimated ranges for shelving were averaged to simplify the cost calculations.

The use of any existing shelving or cabinetry is the least expensive option, but does incur labor costs for disassembly and re-installation that were not estimated into the vault costs. Two layouts, for both fixed and mobile shelving, were estimated based on the number of boxes that could be shelved. For simplicity, the tables show the different layouts as approximately 360CF, 1000CF and 2000CF.

Vapor-Proof Packaging

Vapor-proof packaging can be cost effective, compared to installing RH control for a vault, for small collections where staffing or funding for associated initial labor is available.

Sealed Cabinetry

Sealed cabinetry can be cost effective for a 35°F 8×12 vault, especially if the comparable packaging cost includes the expense of new standard open shelving.

Energy Costs Savings for Vaults Using Microclimate Protection Instead of RH Control

There are substantial annual savings in energy costs earned by not using RH control in a vault. For an 8×12 vault the cost savings may average $850/year ($700/year at 35°F and $1000/year at 25°F). For a 16×24 vault the savings increase to an average of $1500/year ($1300 at 35°F and $1700/year at 25°F). With concerns about increasing energy costs and environmental impact, institutions may consider this an advantage to weigh against the costs and inconvenience of either packaging or sealed cabinetry. It is also advantageous to specify the most energy-efficient equipment for the vault.

Security, Monitoring, Maintenance, and Failure

An important part of any cold-storage program requires implementation of security and monitoring of equipment for proper operation [2]. It is also critical that the unit be linked to a central station monitoring system for the building or have an auto-dialer alarm hookup to an emergency phone number and/or include out-of-range auto-shutoff features for the relevant mechanical equipment. Both freezers and vaults have audible alarms, but remote monitoring is ideal especially where there is no staffing during off hours. Remote monitoring was not included in the cost estimates for freezers and vaults given the unknown variables of each installation.

The least problematic failure of a cold unit is a power outage or total breakdown in the equipment causing shut off and gradual warming to ambient conditions. As long as the cold unit is kept closed and any vapor-sealed packages remain intact, there is generally low risk to the contents. However, should a compressor or chiller fail in a manner that it does not result in total shut down (usually a relay switch malfunction), the unit may heat up inside. Failure of RH-controls can result in RH spikes up to 100%, causing the vault walls and ceilings to weep, and paper boxes to swell with moisture. For this reason some institutions add extra RH protection by using tightly-sealed boxes or plastic sheeting over shelving units and oversized materials.

Conclusions

No single cold storage option is appropriate for all circumstances because institutions have different staffing and operational and capitol budgets that can influence the funding of upfront costs vs. financial commitment to ongoing expenses. Prices will vary among vendors and regions, and there are often additional costs not considered here. Cold storage, especially the use of vaults, requires a commitment to active oversight and maintenance that varies considerably with the chosen storage options.

Institutions must carefully weigh the advantages of one cold storage option over the other based on their circumstances and collection needs. The type(s) of cold storage an institution might select depends on many criteria, as listed in the beginning of this article.

These factors fall into three general categories:

A cost analysis during initial planning helps to clarify the issues unique to each institution, in addition to estimating all the associated expenses for the various options being considered and their sustainability over time. At this initial planning stage staff can discuss in detail the feasibility of each option based on resources and expertise, estimate the costs of the option(s) that seem most practical for their collection, and determine which option(s) can be implemented over time with current resources. Because the cost of cold storage can be daunting, institutions may choose a phased approach, breaking the project into manageable elements to be performed over years, or utilize a combination of several options as either short- or long-term solutions. In many circumstances where the collection size warrants a vault, a multi-phase approach may be the most practical due to the extensive planning, budgeting, and space preparation required for vault installation.

Table 1 Approximate Cost of Leased Space Storage

Storage Volume 20CF 200CF 360 CF 1000 CF 2000 CF
Total # 4×5 negatives; (# boxes) 20,000 (80 boxes) 200,000 (800 boxes) 360,000 (1440 boxes) 1,000,000 (4,000 boxes) 2,000,000 (8,000 boxes)
25F/30% rental costs
Annual Cost/CF/Year Excl. handling/shipping fees $96/CF $90/CF $90/CF <$25/CF <$25/CF
Total annual 25°F cost, excl. fees $1920 $18,000 $32,400 <$25,000 <$50,000
35F/30% rental costs
Annual Cost/CF/Year Excl. handling/shipping fees $75/CF $69/CF $69/CF <$25/CF <$25/CF
Total annual 35°F cost, excl. fees $1500 $13,800 $24,840.00 <$25,000 <$50,000
The leasing rates of a commercial cold storage facility were provided by one vendor with a track record for well-maintained vaults and reliable shipping and handling (Table 1). Because of the variability and efficiency of shelving among formats, large-volume leasing was quoted at a maximum rate. Actual costs for collections with uniform containers or compact containers may be lower. Handling fees will vary with geographic region and usage rates as items are requested, while the variety of formats may influence any fees for the initial shelving/bar coding. Storage volume is based on 4×5 Negatives in boxes (250 items/box) 1000 negatives/CF

 

Table 2 Estimated Annual Operational Costs for Vaults - Energy and Routine Maintenance Costs Only

Vault CF* Shelved Vol. ˜360 CF ˜360 CF ˜360 CF ˜360 CF ˜1000 CF ˜2000 CF ˜1000 CF ˜2000 CF ˜1000 CF ×2000 CF ˜1000 CF ˜2000 CF
Vault 8.5′H Dimensions and Climate 8×12 35°F 35% RH 8×12 35°F No RH control 8×12 25°F/ 35% RH 8×12 25°F No RH control 16×24 35°F/ 35% RH 16×24 35°F No RH control 16×24 25°F 35% RH 16×24 25°F No RH control
Energy Costs @$0.10/KWH $1608/y $912/y $2160/y $1116/y $4368/y $2604/y $4560/y $3204/y
Maintenance Low Estimate $1000/y $1000/y $1000/y $1000/y $1000/y $1000/y $1000/y $1000/y
Total Cost/y w/LOW Estimate $2608/y $1912/y $3160/y $2116/y $5368/y $3604/y $5560/y $4204/y
Total Actual Cost/CF/y w/LOW Estimate $ 3/CF-V $8/CF-S $12/CF-C $2/CF-V $6/CF-S $9/CF-C $ 4/CF-V $10/CF-S $15/CF-C $3/CF-V $7/CF-S $10/CF $2/CF-V $3/CF-S $6/CF-C $1/CF-V $2/CF-S $4/CF-C $2/CF-V $4/CF-S $6/CF-C $1/CF-V $3/CF-S $4/CF-C
Maintenance High Estimate $4000/y $4000/y $4000/y $4000/y $4000/y $4000/y $4000/y $4000/y
Total Cost/y w/HIGH Estimate $5608/y $4912/y $6160/y $5116/y $8368/y $6204/y $8560/y $7204/y
Total Actual Cost/CF/y w/HIGH Estimate $ 7/CF-V $18/CF-S $27/CF-C $6/CF-V $16/CF-S $23/CF-C $ 8/CF-V $20/CF-S $29/CF-C $ 6/CF-V $16/CF-S $24/CF-C $3/CF-V $5/CF-S $9/CF-C $2/CF-V $4/CF-S $7/CF-C $3/CF-V $5/CF-S $9/CF-C $2/CF-V $5/CF-S $7/CF-C
V-vault vol. S-shelved vol. C-cabinet vol. y-year Costs/CF are rounded up or down to nearest $ The estimates in this table include only the costs of energy and maintenance to operate a vault over the course of a year. Both low ($1000/year) and high ($4000/year) annual routine maintenance estimates are provided.
*For an 8×12 vault the total vault volume is 816 CF, with a nominal capacity of 360 CF for mobile open shelving and ˜250 CF for mobile sealed cabinets. For a 16×24 vault the total vault volume is 3264 CF, with a nominal ˜1900 CF for mobile open shelving and ˜1100 CF for mobile sealed cabinets. The actual storage capacity as shelved is 17.5 CF/furniture storage unit using the standard 4×5×12-in. box. The actual capacity of an 8×12 vault is ˜315 CF with mobile open shelving and ˜210 CF with mobile sealed cabinets. The actual capacity of a 16×24 vault is ˜1575 CF for mobile open shelving and 963 CF for mobile sealed cabinets. Cost/CF were calculated using the higher capacity afforded by mobile configurations. Fixed configurations for shelving and cabinets provide less usable storage capacity and would raise the cost/CF by several dollars.

 

Table 3 Cold Storage Costs of Cold Vaults, with Open Standard Shelving and Packaging or Sealed Cabinetry [4×5 Negatives in Boxes (250 items/box) with Shelving 10 boxes (2.5CF)/Shelf, 70 boxes (17.5CF)/Unit]

Vault CF Shelved Vol. 126 ˜360 ˜360 ˜360 ˜360 ˜1000 F ˜1000 F ˜1000 F ˜1000 F
            ˜2000 M ˜2000 M ˜2000 M ˜2000 M
Vault 8.5 Ft H F-Fixed M-Mobile Furniture 6×6 Vestibule 8×12 8×12 8×12 8×12 control 16×24 16×24 control 16×24 16×24 control
  50°F 35°F 35°F 25°F 25°F 35°F 35°F 25°F 25°F
  35% RH 35% RH No RH control 35%RH No RH control 35%RH No RH control 35%RH No RH control
Vault Cost $31,500 $36,830 $22,430 $38,810 $23,420 $73,590 $60,945 $84,600 $63,500
SF Vault 36 96 96 96 96 384 384 384 384
CF Vault Nominal Vol. 306 816 816 816 816 3264 3264 3264 3264
% CF Shelved 50% 44–50% 44–50% 44–50% 44–50% 30–40% F 30–40% F 30–40% F 30–40% F
            ˜60% M ˜60% M ˜60% M ˜60% M
Cost/CF Vault Nominal Vol. $250 $102 $62 $108 $65 $74 F $61 F $85 F $64 F
            $37 M $30 M $43 M $32 M
Actual CF (Usable Vol.) of Shelved Vault (# Boxes) 105 F Fixed + Double -Slider Units 245 F (980) 245 F (980) 245 F (980) 245 F (980) 875 F (3500) 875 F (3500) 875 F (3500) 875 F (3500)
    315 M (1260) 315 M (1260) 315 M (1260) 315 M (1260) 1575 M (6300) 1575 M (6300) 1575 M (6300) 1575 M (6300)
Cost of Open Shelving ˜$1450 6 units $9100–12,000 ($10,500 Ave.) 14 units-F $17,000–32,000 ($24,000 Ave.) 44–55 units-F
    $12,500–16,000 ($14,00 Ave.) 16–19 units-M $69,000–87,000 ($78,000 Ave.) 85–92 units-M
Cost/CF Vault w/New Shelving Actual Vol. $314 F $193 F $134 F $201 F $138 F $112 F $97 F $124 F $100 F
    $161 M $116 M $168 M $119 M $96 M $88 M $103 M $90 M
Cost/CF Packaging $25/hr; 30/day (Cost/box) RH Control Packages not required $34.30 ($8.57) Packages not required $34.30 ($8.57) Packages not required $34.30 ($8.57) Packages not required $34.30 ($8.57)
Cost/CF of Packages w/New Shelving Fixed/Mobile (Cost/box) RH Control Packages not required $77-F ($19) Packages not required $77-F ($19) Packages not required $62-F ($15) Packages not required $62-F ($15)
      $78-M ($20)   $78-M ($20)   $84-M ($21)   $84-M ($21)
Tot. Cost/CF Incl. Vault w/New Shelving & Packages RH Control Packages not required $169 F Packages not required $173 F Packages not required $134 F Packages not required $134 F
      $150 M   $153 M   $124 M   $124 M
Actual CF of Sealed Cabinets (# Boxes) 35 F 158 F (630) 158 F (630) 158 F (630) 158 F (630) 525 F (2100) 525 F (2100) 525 F (2100) 525 F (2100)
    210 M (840) 210 M (840) 210 M (840) 210 M (840) 963 M (3850) 963 M (3850) 963 M (3850) 963 M (3850)
Cabinet Costs ˜$4400 2 units $18,900 (9 units-F) $30,000 (14 units-M) w/estimated mobile installation cost $63,000 (30 units-F) $132,000 (55 units-M) w/estimated mobile installation cost
Cost/CF w/Cabinets (Cost/box) $126 Sealed cabinets not required $119F ($30) $143 M ($36) Sealed cabinets not required $119F ($30) $143 M ($36) Sealed cabinets not required $114F ($29) $137M ($34) Sealed cabinets not required $114F ($29) $137M ($34)
Tot. Cost/CF Incl. Vault w/New Sealed Cabinetry $1026 Sealed cabinets not required $262 F $250 M Sealed cabinets not required $268 F $254 M Sealed cabinets not required $230 F $200 M Sealed cabinets not required $235 F $203 M
BTUH (Est. KWH/yr) 8627 (102) 16831 (160.8) 10980 (91.2) 17328 (216) 11596 (111.6) 38916 (436.8) 27558 (260.4) 44719 (456) 42187 (320.4)
Annual Costs for Energy@ $0.10/KWH $1020/y $1608/y $912/y $2160/y $1116/y $4368/y $2604/y $4560/y $3204/y

 

Table 4 Cold Storage Costs using 20CF Household Freezers (0–25°F) with Vapor-Proof Packaging [4×5 Negatives in Boxes (250 items/box) with 40 boxes (10 CF Materials)/Unit]

CF Freezer Storage 20 CF 200 CF 360 CF 1000 CF 2000 CF
Cost of Freezers $1000 $10,000 $18,000 $50,000 $100,000
# Freezers 1 unit 10 units 18 units 50 units 100 units
SF Floor Space @16 SF/unit w/spacing and aisle in front = 8SF + 8SF 8/8×12 room, 28/16×24 room 16 SF 160 SF 288 SF 800 SF 1600 SF
  3LF 30LF 54 LF 150 LF 300 LF
    8×12 room 16×24 16×24–2 rooms 16×24–4 rooms
CF Actual (Unmodified Interior) 10 CF 100 CF 180 CF 500 CF 1000 CF
Total 4×5 negatives 10,000 100,000 180,000 500,000 1,000,000
# Boxes 40 boxes 400 boxes 720 boxes 2000 boxes 4000 boxes
Cost/CF Nominal Vol. $50/CF $50/CF $50/CF $50/CF $50/CF
Cost/CF Actual Vol. w/boxes $100/CF $100/CF $100/CF $100/CF $100/CF
Cost of Packaging Materials $89 $892 $1368 $3800 $7600
4 boxes/CF $7.60/CF $1.90/box): $1.70/2 bags/box & Sealing Tape and RH Indicators @ $0.20/box $2.23/box $2.23/box $1.90/box $1.90/box $1.90/box
Low-Labor Costs for Packaging $137 $1370 $2469 $6,860 $13,720
GS5 $15/hr, no benefits = $120/day; (×1.1 day) (˜11 days) (˜21 days) (˜57 days) (˜114 days)
5 boxes/hr, 35 boxes/day; $3.43/box $3.43/box $3.43/box $3.43/box $3.43/box $3.43/box
Packaging Costs Materials/Labor $226 $2262 $3837 $10,660 $21,320
Lower-Cost Contract Labor $5.66/box $5.66/box $5.33/box $5.33/box $5.33/box
Estimate $22.64/CF $22.64/CF $21.32/CF $21.32/CF $21.32/CF
Total Freezer/Packaging $1226 $12,262 $21,837 $60,660 $121,320
Low-Cost Labor/20 CF units $61/CF $61/CF $61/CF $61/CF $61/CF
Actual Cost/Usable Volume $122/CF $122/CF $122/CF $122/CF $122/CF
High-Labor for Packaging $267 $2667 $4800 $13,400 $26,800
GS 7 $25/hr incl/benefits=$200/day; (˜1.3 day) (˜13 days) (˜24 days) (˜67 days) (˜133 days)
5 boxes/hr, 30 boxes/day; $6.67/box $6.67/box $6.67/box $6.67/box $6.67/box $6.67/box
Packaging Costs Materials/Labor High-Cost Staff Labor Estimate $356 $3560 $6170 $17,140 $34,267
  $8.90/box $8.90/box $8.57 $8.57 $8.57
  $35.60/CF $35.60/CF $34.28/CF $34.28/CF $34.28/CF
Total Freezer/Packaging Costs $1356 $13,560 $24,170 $57,140 $134,267
High-Cost Labor/20CF unit $68/CF $68/CF $68/CF $68/CF $68/CF
Actual Cost/Usable Volume $136/CF $136/CF $136/CF $136/CF $136/CF
Annual Costs for @$0.10/KWH 600KWH/y/unit=60.00/Unit; Energy Cost/CF/y freezer volume $60/y $600/y $1080/y $3000/y $6000/y
Cost/CF/y actual freezer volume $3/CF/y $3/CF/y $3/CF/y $3/CF/y $3/CF/y
Maintenance costs are negligible $6/CF/y actual $6/CF/y actual $6/CF/y actual $6/CF/y actual $6/CF/y actual
A Sears Kenmore auto-defrost 20.3 CF Household Freezer (˜ $700) was the baseline unit used for this study, along with the Onset HOBO data logger with auto-dialer and remote alarm ($300). Alarm hook-up to a facility-wide monitoring system, where available, costs 2 −3 times more than an auto-dialer (˜$1000.00/unit). Household models tend to be reliable (when rated by consumer groups) and readily available, replaced, and serviced. Large-quantity discounts were not factored into the estimates. Commercial (restaurant and scientific) freezer units are other freezer options and are available in 40 and 70 CF capacities. They were not selected for this study due to several factors including noise, heat, smaller doors, expense, and some reported reliability issues.
The vapor-proof package is based on a design used by the author, incorporating a low-cost, heavyweight (6 or 8 mil) re-sealable polyethylene outer bag and an inner flush-cut bag of translucent polyethylene/polyester laminate with a metallic deposit, both sized for the standard 4×5 “shoebox.” Both bags can be re-used indefinitely until damaged. Also included was clear acrylic 2-inch-wide tape to seal over the flush-cut bag and one RH indicator card per package. These packaging materials are available in bulk from Uline and other vendors. The cost of this packaging is about midway between using two poly bags alone or a polyethylene outer bag with an inner metal foil-laminate plastic bag (such as used at the National Gallery of Art). Due to the durability and high-quality seams of these bags, desiccated paperboard inserts between bags was not estimated due to the greater expense and labor. Shipping costs were not included, but discounts were calculated for larger CF quantities (greater discounts may reduce costs further). Labor for packaging was based on two different levels of packaging productivity and federal hourly rates (GS 5 and 7, Washington, DC region).

 

Table 5 Costs of 25°F Cold Vault No RH-Control: Open Standard Shelving and Packaging vs. Sealed Cabinetry [4×5 Negatives in 4×5×12-in. Boxes, 10 boxes (2.5CF)/Shelf, 70 boxes (17.5CF)/7-shelf Unit]

CF Vault Volume as Shelved ˜360 CF ˜360 CF ˜1000 CF ˜2000 CF
Vault Size 8′×12′×8.5H Fixed Shelving 8′×12′×8.5H Mobile Shelving 16′×24′×8.5′H Fixed Shelving 16′×24′×8.5′H Mobile Shelving
Cost of 25°F Vault w/o RH control $23,420 $23,420 $63,500 $63,500
Nominal Vault Volume (If Shelved) ˜360 CF ˜360 CF ˜1000 CF ˜2000 CF
# Negatives 360,000 360,000 1,000,000 2,000,000
# Boxes 1440 boxes 1440 boxes 4,000 boxes 8,000 boxes
Cost/CF Nominal Volume of Vault $65/CF $65/CF $64/CF $32/CF
Actual Vault Vol. Open Shelving 245 CF actual 315 CF actual 875 CF actual 1575 CF actual
# negatives 245,000 315,000 875,000 1,575,000
#boxes 980 boxes 1260 boxes 3500 boxes 6300 boxes
Cost/CF Actual Vol. of Vault $96/CF $74/CF $73/CF $40/CF
Costs of Materials $1862 $2394 $6650 $11,970
4 boxes/CF $7.60/CF ($1.90/box): $1.70/2 bags/box & Sealing Tape and RH Indicators @ $0.20/box $7.60/CF $7.60/CF $7.60/CF $7.60/CF
High-Cost Labor for Packaging, $6537 $8404 $23,345 $42,021
GS 7 $25/hr = $200/day; 30 boxes/day; (33 days) (42 days) (117) (210)
$6.67/box; ˜$27/CF (#days to package) ˜$27/CF ˜$27/CF ˜$27/CF ˜$27/CF
Packaging Costs Materials/Labor $8,399 $10,798 $29,995 $53,991
Cost/box $8.57/box $8.57/box $8.57/box $8.57/box
Cost/CF $34.30/CF $34.30/CF $34.30/CF $34.30/CF
Cost of New Open Shelving Units $9100–12,000 $12,500–16,000 $17,000–32,000 $69,000–87,000
  ($10,500 ave.) ($14,000 ave.) ($24,000 ave.) ($78,000 ave.)
  14 units 16–19 units (18 ave.) 44–55 units (50 ave.) 85–92 units (90 ave.)
Cost of Packaging w/New Shelving $18,899 $24,798 $53,995 $131,991
Cost/CF $77/CF $78/CF $62/CF $84/CF
Cost/box $19.28/box $19.68/box $15.43/box $20.95/box
Total Vault & Packaging Cost $31,819 $34,218 $93,495 $117,491
w/Re-use of existing shelving $130/CF $109/CF $107/CF $75/CF
Cost/CF; Cost/box $32.47/box $27.16/box $26.71/box $18.65
Total Vault & Packaging Cost $42,310 $48,218 $117,495 $195,491
w/New Shelving Actual Cost $173/CF $153/CF $134/CF $124/CF
Cost/CF; Cost/box $43.17/box $38.27/box $33.57/box $31.03/box
Nominal Cabinet Volume 27.3 CF/Unit 245 CF 328 CF 819 CF 1501 CF
# Negatives 245,000 328,000 819,000 1,501,000
# Boxes 980 boxes 1312 boxes 3276 boxes 6004 boxes
Nominal Cost/CF of Sealed Cabinets $77/CF $91/CF $73/CF $88/CF
Actual Cabinet Vol. 17.5CF/Unit 158 CF actual ˜210 CF actual ˜525CF actual ˜963CF actual
# negatives 157,500 210,000 525,000 962,500
# boxes 630 boxes 840 boxes 2100 boxes 3850 boxes
Cost/CF Actual Volume Cabinets $119/CF $143/CF $114/CF $137/CF
Cost of Sealed Cabinets $18,900 ˜$30,000 $60,000 $132,000
˜$1600.00/unit + freight & installation; (Cost of Mobile Rails Estimated) 9 units@$2100 ea 12 units@$2100ea + ˜$5000 rails est. 30 units@$2000 ea 55 units@$1900 ea + ˜$27,500 rails est.
Cost/box $30.00/box $35.71/box $28.57/box $34.29/box
Total Vault & New Cabinets Cost $42,320 $53,420 $123,500 $195,500
Cost/CF Actual Volume $269/CF $254/CF $235/CF $203/CF
Cost/box $67.25/box $63.50/box $58.75/box $50.75/box
Annual Energy and Maintenance Cost $2116/y low est. $2116/y low est. $4204/y low est. $4204/y low est.
Using low ($1000/y) and high ($4000/y) maintenance estimates $5116/y high est. $5116/y high est. $7204/y high est. $7204/y high est.
Equipment specifications included standard 4-inch thick foam-insulated metal-skinned panels for walls, ceiling, and floor; air-chilled coolers, compressors, condensers, desiccant wheels for RH-controlled vaults, backup units for RH-controlled vaults, light fixtures, delivery, and installation. Fire suppression systems and gaseous air filtration were not estimated. Filtration is desirable when packaging is not used for collections, such as acetate film, that might emit contaminating gasses. For the purpose of determining cooling loads, it was assumed that the vault would be placed in an area with office-type conditions, and that the space did not require modification, had ready access to utilities and that exterior mechanical systems could be located within a 75-foot run line. These and other factors could affect the estimates and overall costs and must be considered minimum approximate costs. Annual routine maintenance costs are listed.
Furniture estimates were provided by suppliers of museum-quality shelving and cabinetry, and included fixed and mobile units delivered and installed. The costs for silicone gasket-sealed cabinets were based on units 39.5″W × 17.5″D × 84″H (Table 4) with seven 12″H shelves. Standard open shelving estimates were based on units 36″W × 12″D × 84″H with seven 12″H shelves. Re-use of any existing shelving or cabinetry is the least expensive option, but does incur labor costs for disassembly and re-installation that were not estimated into the vault costs. Two layouts, for both fixed and mobile shelving, were estimated based on the number of boxes that could be shelved. The installation cost for mobile cabinets was approximated. The cost of buffer materials and labor to condition was NOT estimated.

Acknowledgments

Financial support to assist in research for this article was generously provided by The Andrew W. Mellon Foundation. Much of the information in this article was previously presented in 2003 and 2006 at two Mellon Collaborative Workshops in Photograph Preservation held at the Library of Congress and focused on preventive conservation. Constance McCabe provided excellent editorial assistance for this article, helpful analysis of the costs, and many fruitful discussions over the years concerning the implementation of cold storage. George Charlsen of the Gieseler Corporation (located in Joppa, MD) provided vault quotes and much information. All other vendors asked to remain anonymous. This article could not have been possible without the pro bono estimates provided by the vendors.

References

[1] McCormick-Goodhart, Mark and Wilhelm, Henry. The Design and Operation of a Passive Humidity-Controlled Cold Storage Vault Using Conventional Freezer Technology and Moisture-Sealed Cabinets. IS&T's 2004 Archiving Conference Final Program and Proceedings: 176–182. Also: http://www.wilhelm-research.com/ist/WIR_ISTpaper200404MMG%20preview.htmlPreprints

[2] Wallace, James H. A Case Study - Twenty Years Experience at the Smithsonian Institution: The Planning and Operation of a Cold Storage Facility for Photographs. IS&T's 2004 Archiving Conference Final Program and Proceedings: 172–175.

Papers presented in Topics in Photographic Preservation, Volume Twelve have not undergone a formal process of peer review.